text: /*
   * Copyright (c) 1995, 2019, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2019, Azul Systems, Inc. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.lang;
  
  import java.io.*;
  import java.math.BigInteger;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  import java.util.stream.Collectors;
  import java.util.List;
  import java.util.Optional;
  import java.util.StringTokenizer;
  
  import jdk.internal.access.SharedSecrets;
  import jdk.internal.reflect.CallerSensitive;
  import jdk.internal.reflect.Reflection;
  
  /**
   * Every Java application has a single instance of class
   * {@code Runtime} that allows the application to interface with
   * the environment in which the application is running. The current
   * runtime can be obtained from the {@code getRuntime} method.
   * <p>
   * An application cannot create its own instance of this class.
   *
   * @author  unascribed
   * @see     java.lang.Runtime#getRuntime()
   * @since   1.0
   */
  
  public class Runtime {
      private static final Runtime currentRuntime = new Runtime();
  
      private static Version version;
  
      /**
       * Returns the runtime object associated with the current Java application.
       * Most of the methods of class {@code Runtime} are instance
       * methods and must be invoked with respect to the current runtime object.
       *
       * @return  the {@code Runtime} object associated with the current
       *          Java application.
       */
      public static Runtime getRuntime() {
          return currentRuntime;
      }
  
      /** Don't let anyone else instantiate this class */
      private Runtime() {}
  
      /**
       * Terminates the currently running Java virtual machine by initiating its
       * shutdown sequence.  This method never returns normally.  The argument
       * serves as a status code; by convention, a nonzero status code indicates
       * abnormal termination.
       *
       * <p> All registered {@linkplain #addShutdownHook shutdown hooks}, if any,
       * are started in some unspecified order and allowed to run concurrently
       * until they finish.  Once this is done the virtual machine
       * {@linkplain #halt halts}.
       *
       * <p> If this method is invoked after all shutdown hooks have already
       * been run and the status is nonzero then this method halts the
       * virtual machine with the given status code. Otherwise, this method
       * blocks indefinitely.
       *
       * <p> The {@link System#exit(int) System.exit} method is the
       * conventional and convenient means of invoking this method.
       *
       * @param  status
       *         Termination status.  By convention, a nonzero status code
       *         indicates abnormal termination.
       *
       * @throws SecurityException
       *         If a security manager is present and its
       *         {@link SecurityManager#checkExit checkExit} method does not permit
       *         exiting with the specified status
       *
       * @see java.lang.SecurityException
       * @see java.lang.SecurityManager#checkExit(int)
       * @see #addShutdownHook
       * @see #removeShutdownHook
       * @see #halt(int)
       */
      public void exit(int status) {
          SecurityManager security = System.getSecurityManager();
          if (security != null) {
              security.checkExit(status);
          }
          Shutdown.exit(status);
      }
  
      /**
       * Registers a new virtual-machine shutdown hook.
       *
       * <p> The Java virtual machine <i>shuts down</i> in response to two kinds
       * of events:
       *
       *   <ul>
       *
       *   <li> The program <i>exits</i> normally, when the last non-daemon
       *   thread exits or when the {@link #exit exit} (equivalently,
       *   {@link System#exit(int) System.exit}) method is invoked, or
       *
       *   <li> The virtual machine is <i>terminated</i> in response to a
       *   user interrupt, such as typing {@code ^C}, or a system-wide event,
       *   such as user logoff or system shutdown.
       *
       *   </ul>
       *
       * <p> A <i>shutdown hook</i> is simply an initialized but unstarted
       * thread.  When the virtual machine begins its shutdown sequence it will
       * start all registered shutdown hooks in some unspecified order and let
       * them run concurrently.  When all the hooks have finished it will then
       * halt. Note that daemon threads will continue to run during the shutdown
       * sequence, as will non-daemon threads if shutdown was initiated by
       * invoking the {@link #exit exit} method.
       *
       * <p> Once the shutdown sequence has begun it can be stopped only by
       * invoking the {@link #halt halt} method, which forcibly
       * terminates the virtual machine.
       *
       * <p> Once the shutdown sequence has begun it is impossible to register a
       * new shutdown hook or de-register a previously-registered hook.
       * Attempting either of these operations will cause an
       * {@link IllegalStateException} to be thrown.
       *
       * <p> Shutdown hooks run at a delicate time in the life cycle of a virtual
       * machine and should therefore be coded defensively.  They should, in
       * particular, be written to be thread-safe and to avoid deadlocks insofar
       * as possible.  They should also not rely blindly upon services that may
       * have registered their own shutdown hooks and therefore may themselves in
       * the process of shutting down.  Attempts to use other thread-based
       * services such as the AWT event-dispatch thread, for example, may lead to
       * deadlocks.
       *
       * <p> Shutdown hooks should also finish their work quickly.  When a
       * program invokes {@link #exit exit} the expectation is
       * that the virtual machine will promptly shut down and exit.  When the
       * virtual machine is terminated due to user logoff or system shutdown the
       * underlying operating system may only allow a fixed amount of time in
       * which to shut down and exit.  It is therefore inadvisable to attempt any
       * user interaction or to perform a long-running computation in a shutdown
       * hook.
       *
       * <p> Uncaught exceptions are handled in shutdown hooks just as in any
       * other thread, by invoking the
       * {@link ThreadGroup#uncaughtException uncaughtException} method of the
       * thread's {@link ThreadGroup} object. The default implementation of this
       * method prints the exception's stack trace to {@link System#err} and
       * terminates the thread; it does not cause the virtual machine to exit or
       * halt.
       *
       * <p> In rare circumstances the virtual machine may <i>abort</i>, that is,
       * stop running without shutting down cleanly.  This occurs when the
       * virtual machine is terminated externally, for example with the
       * {@code SIGKILL} signal on Unix or the {@code TerminateProcess} call on
       * Microsoft Windows.  The virtual machine may also abort if a native
       * method goes awry by, for example, corrupting internal data structures or
       * attempting to access nonexistent memory.  If the virtual machine aborts
       * then no guarantee can be made about whether or not any shutdown hooks
       * will be run.
       *
       * @param   hook
       *          An initialized but unstarted {@link Thread} object
       *
       * @throws  IllegalArgumentException
       *          If the specified hook has already been registered,
       *          or if it can be determined that the hook is already running or
       *          has already been run
       *
       * @throws  IllegalStateException
       *          If the virtual machine is already in the process
       *          of shutting down
       *
       * @throws  SecurityException
       *          If a security manager is present and it denies
       *          {@link RuntimePermission}("shutdownHooks")
       *
       * @see #removeShutdownHook
       * @see #halt(int)
       * @see #exit(int)
       * @since 1.3
       */
      public void addShutdownHook(Thread hook) {
          SecurityManager sm = System.getSecurityManager();
          if (sm != null) {
              sm.checkPermission(new RuntimePermission("shutdownHooks"));
          }
          ApplicationShutdownHooks.add(hook);
      }
  
      /**
       * De-registers a previously-registered virtual-machine shutdown hook.
       *
       * @param hook the hook to remove
       * @return {@code true} if the specified hook had previously been
       * registered and was successfully de-registered, {@code false}
       * otherwise.
       *
       * @throws  IllegalStateException
       *          If the virtual machine is already in the process of shutting
       *          down
       *
       * @throws  SecurityException
       *          If a security manager is present and it denies
       *          {@link RuntimePermission}("shutdownHooks")
       *
       * @see #addShutdownHook
       * @see #exit(int)
       * @since 1.3
       */
      public boolean removeShutdownHook(Thread hook) {
          SecurityManager sm = System.getSecurityManager();
          if (sm != null) {
              sm.checkPermission(new RuntimePermission("shutdownHooks"));
          }
          return ApplicationShutdownHooks.remove(hook);
      }
  
      /**
       * Forcibly terminates the currently running Java virtual machine.  This
       * method never returns normally.
       *
       * <p> This method should be used with extreme caution.  Unlike the
       * {@link #exit exit} method, this method does not cause shutdown
       * hooks to be started.  If the shutdown sequence has already been
       * initiated then this method does not wait for any running
       * shutdown hooks to finish their work.
       *
       * @param  status
       *         Termination status. By convention, a nonzero status code
       *         indicates abnormal termination. If the {@link Runtime#exit exit}
       *         (equivalently, {@link System#exit(int) System.exit}) method
       *         has already been invoked then this status code
       *         will override the status code passed to that method.
       *
       * @throws SecurityException
       *         If a security manager is present and its
       *         {@link SecurityManager#checkExit checkExit} method
       *         does not permit an exit with the specified status
       *
       * @see #exit
       * @see #addShutdownHook
       * @see #removeShutdownHook
       * @since 1.3
       */
      public void halt(int status) {
          SecurityManager sm = System.getSecurityManager();
          if (sm != null) {
              sm.checkExit(status);
          }
          Shutdown.beforeHalt();
          Shutdown.halt(status);
      }
  
      /**
       * Executes the specified string command in a separate process.
       *
       * <p>This is a convenience method.  An invocation of the form
       * {@code exec(command)}
       * behaves in exactly the same way as the invocation
       * {@link #exec(String, String[], File) exec}{@code (command, null, null)}.
       *
       * @param   command   a specified system command.
       *
       * @return  A new {@link Process} object for managing the subprocess
       *
       * @throws  SecurityException
       *          If a security manager exists and its
       *          {@link SecurityManager#checkExec checkExec}
       *          method doesn't allow creation of the subprocess
       *
       * @throws  IOException
       *          If an I/O error occurs
       *
       * @throws  NullPointerException
       *          If {@code command} is {@code null}
       *
       * @throws  IllegalArgumentException
       *          If {@code command} is empty
       *
       * @see     #exec(String[], String[], File)
       * @see     ProcessBuilder
       */
      public Process exec(String command) throws IOException {
          return exec(command, null, null);
      }
  
      /**
       * Executes the specified string command in a separate process with the
       * specified environment.
       *
       * <p>This is a convenience method.  An invocation of the form
       * {@code exec(command, envp)}
       * behaves in exactly the same way as the invocation
       * {@link #exec(String, String[], File) exec}{@code (command, envp, null)}.
       *
       * @param   command   a specified system command.
       *
       * @param   envp      array of strings, each element of which
       *                    has environment variable settings in the format
       *                    <i>name</i>=<i>value</i>, or
       *                    {@code null} if the subprocess should inherit
       *                    the environment of the current process.
       *
       * @return  A new {@link Process} object for managing the subprocess
       *
       * @throws  SecurityException
       *          If a security manager exists and its
       *          {@link SecurityManager#checkExec checkExec}
       *          method doesn't allow creation of the subprocess
       *
       * @throws  IOException
       *          If an I/O error occurs
       *
       * @throws  NullPointerException
       *          If {@code command} is {@code null},
       *          or one of the elements of {@code envp} is {@code null}
       *
       * @throws  IllegalArgumentException
       *          If {@code command} is empty
       *
       * @see     #exec(String[], String[], File)
       * @see     ProcessBuilder
       */
      public Process exec(String command, String[] envp) throws IOException {
          return exec(command, envp, null);
      }
  
      /**
       * Executes the specified string command in a separate process with the
       * specified environment and working directory.
       *
       * <p>This is a convenience method.  An invocation of the form
       * {@code exec(command, envp, dir)}
       * behaves in exactly the same way as the invocation
       * {@link #exec(String[], String[], File) exec}{@code (cmdarray, envp, dir)},
       * where {@code cmdarray} is an array of all the tokens in
       * {@code command}.
       *
       * <p>More precisely, the {@code command} string is broken
       * into tokens using a {@link StringTokenizer} created by the call
       * {@code new {@link StringTokenizer}(command)} with no
       * further modification of the character categories.  The tokens
       * produced by the tokenizer are then placed in the new string
       * array {@code cmdarray}, in the same order.
       *
       * @param   command   a specified system command.
       *
       * @param   envp      array of strings, each element of which
       *                    has environment variable settings in the format
       *                    <i>name</i>=<i>value</i>, or
       *                    {@code null} if the subprocess should inherit
       *                    the environment of the current process.
       *
       * @param   dir       the working directory of the subprocess, or
       *                    {@code null} if the subprocess should inherit
       *                    the working directory of the current process.
       *
       * @return  A new {@link Process} object for managing the subprocess
       *
       * @throws  SecurityException
       *          If a security manager exists and its
       *          {@link SecurityManager#checkExec checkExec}
       *          method doesn't allow creation of the subprocess
       *
       * @throws  IOException
       *          If an I/O error occurs
       *
       * @throws  NullPointerException
       *          If {@code command} is {@code null},
       *          or one of the elements of {@code envp} is {@code null}
       *
       * @throws  IllegalArgumentException
       *          If {@code command} is empty
       *
       * @see     ProcessBuilder
       * @since 1.3
       */
      public Process exec(String command, String[] envp, File dir)
          throws IOException {
          if (command.isEmpty())
              throw new IllegalArgumentException("Empty command");
  
          StringTokenizer st = new StringTokenizer(command);
          String[] cmdarray = new String[st.countTokens()];
          for (int i = 0; st.hasMoreTokens(); i++)
              cmdarray[i] = st.nextToken();
          return exec(cmdarray, envp, dir);
      }
  
      /**
       * Executes the specified command and arguments in a separate process.
       *
       * <p>This is a convenience method.  An invocation of the form
       * {@code exec(cmdarray)}
       * behaves in exactly the same way as the invocation
       * {@link #exec(String[], String[], File) exec}{@code (cmdarray, null, null)}.
       *
       * @param   cmdarray  array containing the command to call and
       *                    its arguments.
       *
       * @return  A new {@link Process} object for managing the subprocess
       *
       * @throws  SecurityException
       *          If a security manager exists and its
       *          {@link SecurityManager#checkExec checkExec}
       *          method doesn't allow creation of the subprocess
       *
       * @throws  IOException
       *          If an I/O error occurs
       *
       * @throws  NullPointerException
       *          If {@code cmdarray} is {@code null},
       *          or one of the elements of {@code cmdarray} is {@code null}
       *
       * @throws  IndexOutOfBoundsException
       *          If {@code cmdarray} is an empty array
       *          (has length {@code 0})
       *
       * @see     ProcessBuilder
       */
      public Process exec(String cmdarray[]) throws IOException {
          return exec(cmdarray, null, null);
      }
  
      /**
       * Executes the specified command and arguments in a separate process
       * with the specified environment.
       *
       * <p>This is a convenience method.  An invocation of the form
       * {@code exec(cmdarray, envp)}
       * behaves in exactly the same way as the invocation
       * {@link #exec(String[], String[], File) exec}{@code (cmdarray, envp, null)}.
       *
       * @param   cmdarray  array containing the command to call and
       *                    its arguments.
       *
       * @param   envp      array of strings, each element of which
       *                    has environment variable settings in the format
       *                    <i>name</i>=<i>value</i>, or
       *                    {@code null} if the subprocess should inherit
       *                    the environment of the current process.
       *
       * @return  A new {@link Process} object for managing the subprocess
       *
       * @throws  SecurityException
       *          If a security manager exists and its
       *          {@link SecurityManager#checkExec checkExec}
       *          method doesn't allow creation of the subprocess
       *
       * @throws  IOException
       *          If an I/O error occurs
       *
       * @throws  NullPointerException
       *          If {@code cmdarray} is {@code null},
       *          or one of the elements of {@code cmdarray} is {@code null},
       *          or one of the elements of {@code envp} is {@code null}
       *
       * @throws  IndexOutOfBoundsException
       *          If {@code cmdarray} is an empty array
       *          (has length {@code 0})
       *
       * @see     ProcessBuilder
       */
      public Process exec(String[] cmdarray, String[] envp) throws IOException {
          return exec(cmdarray, envp, null);
      }
  
  
      /**
       * Executes the specified command and arguments in a separate process with
       * the specified environment and working directory.
       *
       * <p>Given an array of strings {@code cmdarray}, representing the
       * tokens of a command line, and an array of strings {@code envp},
       * representing "environment" variable settings, this method creates
       * a new process in which to execute the specified command.
       *
       * <p>This method checks that {@code cmdarray} is a valid operating
       * system command.  Which commands are valid is system-dependent,
       * but at the very least the command must be a non-empty list of
       * non-null strings.
       *
       * <p>If {@code envp} is {@code null}, the subprocess inherits the
       * environment settings of the current process.
       *
       * <p>A minimal set of system dependent environment variables may
       * be required to start a process on some operating systems.
       * As a result, the subprocess may inherit additional environment variable
       * settings beyond those in the specified environment.
       *
       * <p>{@link ProcessBuilder#start()} is now the preferred way to
       * start a process with a modified environment.
       *
       * <p>The working directory of the new subprocess is specified by {@code dir}.
       * If {@code dir} is {@code null}, the subprocess inherits the
       * current working directory of the current process.
       *
       * <p>If a security manager exists, its
       * {@link SecurityManager#checkExec checkExec}
       * method is invoked with the first component of the array
       * {@code cmdarray} as its argument. This may result in a
       * {@link SecurityException} being thrown.
       *
       * <p>Starting an operating system process is highly system-dependent.
       * Among the many things that can go wrong are:
       * <ul>
       * <li>The operating system program file was not found.
       * <li>Access to the program file was denied.
       * <li>The working directory does not exist.
       * </ul>
       *
       * <p>In such cases an exception will be thrown.  The exact nature
       * of the exception is system-dependent, but it will always be a
       * subclass of {@link IOException}.
       *
       * <p>If the operating system does not support the creation of
       * processes, an {@link UnsupportedOperationException} will be thrown.
       *
       *
       * @param   cmdarray  array containing the command to call and
       *                    its arguments.
       *
       * @param   envp      array of strings, each element of which
       *                    has environment variable settings in the format
       *                    <i>name</i>=<i>value</i>, or
       *                    {@code null} if the subprocess should inherit
       *                    the environment of the current process.
       *
       * @param   dir       the working directory of the subprocess, or
       *                    {@code null} if the subprocess should inherit
       *                    the working directory of the current process.
       *
       * @return  A new {@link Process} object for managing the subprocess
       *
       * @throws  SecurityException
       *          If a security manager exists and its
       *          {@link SecurityManager#checkExec checkExec}
       *          method doesn't allow creation of the subprocess
       *
       * @throws  UnsupportedOperationException
       *          If the operating system does not support the creation of processes.
       *
       * @throws  IOException
       *          If an I/O error occurs
       *
       * @throws  NullPointerException
       *          If {@code cmdarray} is {@code null},
       *          or one of the elements of {@code cmdarray} is {@code null},
       *          or one of the elements of {@code envp} is {@code null}
       *
       * @throws  IndexOutOfBoundsException
       *          If {@code cmdarray} is an empty array
       *          (has length {@code 0})
       *
       * @see     ProcessBuilder
       * @since 1.3
       */
      public Process exec(String[] cmdarray, String[] envp, File dir)
          throws IOException {
          return new ProcessBuilder(cmdarray)
              .environment(envp)
              .directory(dir)
              .start();
      }
  
      /**
       * Returns the number of processors available to the Java virtual machine.
       *
       * <p> This value may change during a particular invocation of the virtual
       * machine.  Applications that are sensitive to the number of available
       * processors should therefore occasionally poll this property and adjust
       * their resource usage appropriately. </p>
       *
       * @return  the maximum number of processors available to the virtual
       *          machine; never smaller than one
       * @since 1.4
       */
      public native int availableProcessors();
  
      /**
       * Returns the amount of free memory in the Java Virtual Machine.
       * Calling the
       * {@code gc} method may result in increasing the value returned
       * by {@code freeMemory.}
       *
       * @return  an approximation to the total amount of memory currently
       *          available for future allocated objects, measured in bytes.
       */
      public native long freeMemory();
  
      /**
       * Returns the total amount of memory in the Java virtual machine.
       * The value returned by this method may vary over time, depending on
       * the host environment.
       * <p>
       * Note that the amount of memory required to hold an object of any
       * given type may be implementation-dependent.
       *
       * @return  the total amount of memory currently available for current
       *          and future objects, measured in bytes.
       */
      public native long totalMemory();
  
      /**
       * Returns the maximum amount of memory that the Java virtual machine
       * will attempt to use.  If there is no inherent limit then the value
       * {@link java.lang.Long#MAX_VALUE} will be returned.
       *
       * @return  the maximum amount of memory that the virtual machine will
       *          attempt to use, measured in bytes
       * @since 1.4
       */
      public native long maxMemory();
  
      /**
       * Runs the garbage collector in the Java Virtual Machine.
       * <p>
       * Calling this method suggests that the Java Virtual Machine
       * expend effort toward recycling unused objects in order to
       * make the memory they currently occupy available for reuse
       * by the Java Virtual Machine.
       * When control returns from the method call, the Java Virtual Machine
       * has made a best effort to reclaim space from all unused objects.
       * There is no guarantee that this effort will recycle any particular
       * number of unused objects, reclaim any particular amount of space, or
       * complete at any particular time, if at all, before the method returns or ever.
       * <p>
       * The name {@code gc} stands for "garbage
       * collector". The Java Virtual Machine performs this recycling
       * process automatically as needed, in a separate thread, even if the
       * {@code gc} method is not invoked explicitly.
       * <p>
       * The method {@link System#gc()} is the conventional and convenient
       * means of invoking this method.
       */
      public native void gc();
  
      /**
       * Runs the finalization methods of any objects pending finalization.
       * Calling this method suggests that the Java virtual machine expend
       * effort toward running the {@code finalize} methods of objects
       * that have been found to be discarded but whose {@code finalize}
       * methods have not yet been run. When control returns from the
       * method call, the virtual machine has made a best effort to
       * complete all outstanding finalizations.
       * <p>
       * The virtual machine performs the finalization process
       * automatically as needed, in a separate thread, if the
       * {@code runFinalization} method is not invoked explicitly.
       * <p>
       * The method {@link System#runFinalization()} is the conventional
       * and convenient means of invoking this method.
       *
       * @see     java.lang.Object#finalize()
       */
      public void runFinalization() {
          SharedSecrets.getJavaLangRefAccess().runFinalization();
      }
  
      /**
       * Loads the native library specified by the filename argument.  The filename
       * argument must be an absolute path name.
       * (for example
       * {@code Runtime.getRuntime().load("/home/avh/lib/libX11.so");}).
       *
       * If the filename argument, when stripped of any platform-specific library
       * prefix, path, and file extension, indicates a library whose name is,
       * for example, L, and a native library called L is statically linked
       * with the VM, then the JNI_OnLoad_L function exported by the library
       * is invoked rather than attempting to load a dynamic library.
       * A filename matching the argument does not have to exist in the file
       * system.
       * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
       * for more details.
       *
       * Otherwise, the filename argument is mapped to a native library image in
       * an implementation-dependent manner.
       * <p>
       * First, if there is a security manager, its {@code checkLink}
       * method is called with the {@code filename} as its argument.
       * This may result in a security exception.
       * <p>
       * This is similar to the method {@link #loadLibrary(String)}, but it
       * accepts a general file name as an argument rather than just a library
       * name, allowing any file of native code to be loaded.
       * <p>
       * The method {@link System#load(String)} is the conventional and
       * convenient means of invoking this method.
       *
       * @param      filename   the file to load.
       * @throws     SecurityException  if a security manager exists and its
       *             {@code checkLink} method doesn't allow
       *             loading of the specified dynamic library
       * @throws     UnsatisfiedLinkError  if either the filename is not an
       *             absolute path name, the native library is not statically
       *             linked with the VM, or the library cannot be mapped to
       *             a native library image by the host system.
       * @throws     NullPointerException if {@code filename} is
       *             {@code null}
       * @see        java.lang.Runtime#getRuntime()
       * @see        java.lang.SecurityException
       * @see        java.lang.SecurityManager#checkLink(java.lang.String)
       */
      @CallerSensitive
      public void load(String filename) {
          load0(Reflection.getCallerClass(), filename);
      }
  
      void load0(Class<?> fromClass, String filename) {
          SecurityManager security = System.getSecurityManager();
          if (security != null) {
              security.checkLink(filename);
          }
          if (!(new File(filename).isAbsolute())) {
              throw new UnsatisfiedLinkError(
                  "Expecting an absolute path of the library: " + filename);
          }
          ClassLoader.loadLibrary(fromClass, filename, true);
      }
  
      /**
       * Loads the native library specified by the {@code libname}
       * argument.  The {@code libname} argument must not contain any platform
       * specific prefix, file extension or path. If a native library
       * called {@code libname} is statically linked with the VM, then the
       * JNI_OnLoad_{@code libname} function exported by the library is invoked.
       * See the <a href="{@docRoot}/../specs/jni/index.html"> JNI Specification</a>
       * for more details.
       *
       * Otherwise, the libname argument is loaded from a system library
       * location and mapped to a native library image in an implementation-
       * dependent manner.
       * <p>
       * First, if there is a security manager, its {@code checkLink}
       * method is called with the {@code libname} as its argument.
       * This may result in a security exception.
       * <p>
       * The method {@link System#loadLibrary(String)} is the conventional
       * and convenient means of invoking this method. If native
       * methods are to be used in the implementation of a class, a standard
       * strategy is to put the native code in a library file (call it
       * {@code LibFile}) and then to put a static initializer:
       * <blockquote><pre>
       * static { System.loadLibrary("LibFile"); }
       * </pre></blockquote>
       * within the class declaration. When the class is loaded and
       * initialized, the necessary native code implementation for the native
       * methods will then be loaded as well.
       * <p>
       * If this method is called more than once with the same library
       * name, the second and subsequent calls are ignored.
       *
       * @param      libname   the name of the library.
       * @throws     SecurityException  if a security manager exists and its
       *             {@code checkLink} method doesn't allow
       *             loading of the specified dynamic library
       * @throws     UnsatisfiedLinkError if either the libname argument
       *             contains a file path, the native library is not statically
       *             linked with the VM,  or the library cannot be mapped to a
       *             native library image by the host system.
       * @throws     NullPointerException if {@code libname} is
       *             {@code null}
       * @see        java.lang.SecurityException
       * @see        java.lang.SecurityManager#checkLink(java.lang.String)
       */
      @CallerSensitive
      public void loadLibrary(String libname) {
          loadLibrary0(Reflection.getCallerClass(), libname);
      }
  
      void loadLibrary0(Class<?> fromClass, String libname) {
          SecurityManager security = System.getSecurityManager();
          if (security != null) {
              security.checkLink(libname);
          }
          if (libname.indexOf((int)File.separatorChar) != -1) {
              throw new UnsatisfiedLinkError(
                  "Directory separator should not appear in library name: " + libname);
          }
          ClassLoader.loadLibrary(fromClass, libname, false);
      }
  
      /**
       * Returns the version of the Java Runtime Environment as a {@link Version}.
       *
       * @return  the {@link Version} of the Java Runtime Environment
       *
       * @since  9
       */
      public static Version version() {
          if (version == null) {
              version = new Version(VersionProps.versionNumbers(),
                      VersionProps.pre(), VersionProps.build(),
                      VersionProps.optional());
          }
          return version;
      }
  
      /**
       * A representation of a version string for an implementation of the
       * Java&nbsp;SE Platform.  A version string consists of a version number
       * optionally followed by pre-release and build information.
       *
       * <h2><a id="verNum">Version numbers</a></h2>
       *
       * <p> A <em>version number</em>, {@code $VNUM}, is a non-empty sequence of
       * elements separated by period characters (U+002E).  An element is either
       * zero, or an unsigned integer numeral without leading zeros.  The final
       * element in a version number must not be zero.  When an element is
       * incremented, all subsequent elements are removed.  The format is: </p>
       *
       * <blockquote><pre>
       * [1-9][0-9]*((\.0)*\.[1-9][0-9]*)*
       * </pre></blockquote>
       *
       * <p> The sequence may be of arbitrary length but the first four elements
       * are assigned specific meanings, as follows:</p>
       *
       * <blockquote><pre>
       * $FEATURE.$INTERIM.$UPDATE.$PATCH
       * </pre></blockquote>
       *
       * <ul>
       *
       * <li><p> <a id="FEATURE">{@code $FEATURE}</a> &#x2014; The
       * feature-release counter, incremented for every feature release
       * regardless of release content.  Features may be added in a feature
       * release; they may also be removed, if advance notice was given at least
       * one feature release ahead of time.  Incompatible changes may be made
       * when justified. </p></li>
       *
       * <li><p> <a id="INTERIM">{@code $INTERIM}</a> &#x2014; The
       * interim-release counter, incremented for non-feature releases that
       * contain compatible bug fixes and enhancements but no incompatible
       * changes, no feature removals, and no changes to standard APIs.
       * </p></li>
       *
       * <li><p> <a id="UPDATE">{@code $UPDATE}</a> &#x2014; The update-release
       * counter, incremented for compatible update releases that fix security
       * issues, regressions, and bugs in newer features. </p></li>
       *
       * <li><p> <a id="PATCH">{@code $PATCH}</a> &#x2014; The emergency
       * patch-release counter, incremented only when it's necessary to produce
       * an emergency release to fix a critical issue. </p></li>
       *
       * </ul>
       *
       * <p> The fifth and later elements of a version number are free for use by
       * platform implementors, to identify implementor-specific patch
       * releases. </p>
       *
       * <p> A version number never has trailing zero elements.  If an element
       * and all those that follow it logically have the value zero then all of
       * them are omitted. </p>
       *
       * <p> The sequence of numerals in a version number is compared to another
       * such sequence in numerical, pointwise fashion; <em>e.g.</em>, {@code
       * 10.0.4} is less than {@code 10.1.2}.  If one sequence is shorter than
       * another then the missing elements of the shorter sequence are considered
       * to be less than the corresponding elements of the longer sequence;
       * <em>e.g.</em>, {@code 10.0.2} is less than {@code 10.0.2.1}. </p>
       *
       * <h2><a id="verStr">Version strings</a></h2>
       *
       * <p> A <em>version string</em>, {@code $VSTR}, is a version number {@code
       * $VNUM}, as described above, optionally followed by pre-release and build
       * information, in one of the following formats: </p>
       *
       * <blockquote><pre>
       *     $VNUM(-$PRE)?\+$BUILD(-$OPT)?
       *     $VNUM-$PRE(-$OPT)?
       *     $VNUM(\+-$OPT)?
       * </pre></blockquote>
       *
       * <p> where: </p>
       *
       * <ul>
       *
       * <li><p> <a id="pre">{@code $PRE}</a>, matching {@code ([a-zA-Z0-9]+)}
       * &#x2014; A pre-release identifier.  Typically {@code ea}, for a
       * potentially unstable early-access release under active development, or
       * {@code internal}, for an internal developer build. </p></li>
       *
       * <li><p> <a id="build">{@code $BUILD}</a>, matching {@code
       * (0|[1-9][0-9]*)} &#x2014; The build number, incremented for each promoted
       * build.  {@code $BUILD} is reset to {@code 1} when any portion of {@code
       * $VNUM} is incremented. </p></li>
       *
       * <li><p> <a id="opt">{@code $OPT}</a>, matching {@code ([-a-zA-Z0-9.]+)}
       * &#x2014; Additional build information, if desired.  In the case of an
       * {@code internal} build this will often contain the date and time of the
       * build. </p></li>
       *
       * </ul>
       *
       * <p> A version string {@code 10-ea} matches {@code $VNUM = "10"} and
       * {@code $PRE = "ea"}.  The version string {@code 10+-ea} matches
       * {@code $VNUM = "10"} and {@code $OPT = "ea"}. </p>
       *
       * <p> When comparing two version strings, the value of {@code $OPT}, if
       * present, may or may not be significant depending on the chosen
       * comparison method.  The comparison methods {@link #compareTo(Version)
       * compareTo()} and {@link #compareToIgnoreOptional(Version)
       * compareToIgnoreOptional()} should be used consistently with the
       * corresponding methods {@link #equals(Object) equals()} and {@link
       * #equalsIgnoreOptional(Object) equalsIgnoreOptional()}.  </p>
       *
       * <p> A <em>short version string</em>, {@code $SVSTR}, often useful in
       * less formal contexts, is a version number optionally followed by a
       * pre-release identifier:</p>
       *
       * <blockquote><pre>
       *     $VNUM(-$PRE)?
       * </pre></blockquote>
       *
       * <p>This is a <a href="./doc-files/ValueBased.html">value-based</a>
       * class; use of identity-sensitive operations (including reference equality
       * ({@code ==}), identity hash code, or synchronization) on instances of
       * {@code Version} may have unpredictable results and should be avoided.
       * </p>
       *
       * @since  9
       */
      public static final class Version
          implements Comparable<Version>
      {
          private final List<Integer>     version;
          private final Optional<String>  pre;
          private final Optional<Integer> build;
          private final Optional<String>  optional;
  
          /*
           * List of version number components passed to this constructor MUST
           * be at least unmodifiable (ideally immutable). In the case on an
           * unmodifiable list, the caller MUST hand the list over to this
           * constructor and never change the underlying list.
           */
          private Version(List<Integer> unmodifiableListOfVersions,
                          Optional<String> pre,
                          Optional<Integer> build,
                          Optional<String> optional)
          {
              this.version = unmodifiableListOfVersions;
              this.pre = pre;
              this.build = build;
              this.optional = optional;
          }
  
          /**
           * Parses the given string as a valid
           * <a href="#verStr">version string</a> containing a
           * <a href="#verNum">version number</a> followed by pre-release and
           * build information.
           *
           * @param  s
           *         A string to interpret as a version
           *
           * @throws  IllegalArgumentException
           *          If the given string cannot be interpreted as a valid
           *          version
           *
           * @throws  NullPointerException
           *          If the given string is {@code null}
           *
           * @throws  NumberFormatException
           *          If an element of the version number or the build number
           *          cannot be represented as an {@link Integer}
           *
           * @return  The Version of the given string
           */
          public static Version parse(String s) {
              if (s == null)
                  throw new NullPointerException();
  
              // Shortcut to avoid initializing VersionPattern when creating
              // feature-version constants during startup
              if (isSimpleNumber(s)) {
                  return new Version(List.of(Integer.parseInt(s)),
                          Optional.empty(), Optional.empty(), Optional.empty());
              }
              Matcher m = VersionPattern.VSTR_PATTERN.matcher(s);
              if (!m.matches())
                  throw new IllegalArgumentException("Invalid version string: '"
                                                     + s + "'");
  
              // $VNUM is a dot-separated list of integers of arbitrary length
              String[] split = m.group(VersionPattern.VNUM_GROUP).split("\\.");
              Integer[] version = new Integer[split.length];
              for (int i = 0; i < split.length; i++) {
                  version[i] = Integer.parseInt(split[i]);
              }
  
              Optional<String> pre = Optional.ofNullable(
                      m.group(VersionPattern.PRE_GROUP));
  
              String b = m.group(VersionPattern.BUILD_GROUP);
              // $BUILD is an integer
              Optional<Integer> build = (b == null)
                  ? Optional.empty()
                  : Optional.of(Integer.parseInt(b));
  
              Optional<String> optional = Optional.ofNullable(
                      m.group(VersionPattern.OPT_GROUP));
  
              // empty '+'
              if (!build.isPresent()) {
                  if (m.group(VersionPattern.PLUS_GROUP) != null) {
                      if (optional.isPresent()) {
                          if (pre.isPresent())
                              throw new IllegalArgumentException("'+' found with"
                                  + " pre-release and optional components:'" + s
                                  + "'");
                      } else {
                          throw new IllegalArgumentException("'+' found with neither"
                              + " build or optional components: '" + s + "'");
                      }
                  } else {
                      if (optional.isPresent() && !pre.isPresent()) {
                          throw new IllegalArgumentException("optional component"
                              + " must be preceeded by a pre-release component"
                              + " or '+': '" + s + "'");
                      }
                  }
              }
              return new Version(List.of(version), pre, build, optional);
          }
  
          private static boolean isSimpleNumber(String s) {
              for (int i = 0; i < s.length(); i++) {
                  char c = s.charAt(i);
                  char lowerBound = (i > 0) ? '0' : '1';
                  if (c < lowerBound || c > '9') {
                      return false;
                  }
              }
              return true;
          }
  
          /**
           * Returns the value of the <a href="#FEATURE">feature</a> element of
           * the version number.
           *
           * @return The value of the feature element
           *
           * @since 10
           */
          public int feature() {
              return version.get(0);
          }
  
          /**
           * Returns the value of the <a href="#INTERIM">interim</a> element of
           * the version number, or zero if it is absent.
           *
           * @return The value of the interim element, or zero
           *
           * @since 10
           */
          public int interim() {
              return (version.size() > 1 ? version.get(1) : 0);
          }
  
          /**
           * Returns the value of the <a href="#UPDATE">update</a> element of the
           * version number, or zero if it is absent.
           *
           * @return The value of the update element, or zero
           *
           * @since 10
           */
          public int update() {
              return (version.size() > 2 ? version.get(2) : 0);
          }
  
          /**
           * Returns the value of the <a href="#PATCH">patch</a> element of the
           * version number, or zero if it is absent.
           *
           * @return The value of the patch element, or zero
           *
           * @since 10
           */
          public int patch() {
              return (version.size() > 3 ? version.get(3) : 0);
          }
  
          /**
           * Returns the value of the major element of the version number.
           *
           * @deprecated As of Java&nbsp;SE 10, the first element of a version
           * number is not the major-release number but the feature-release
           * counter, incremented for every time-based release.  Use the {@link
           * #feature()} method in preference to this method.  For compatibility,
           * this method returns the value of the <a href="#FEATURE">feature</a>
           * element.
           *
           * @return The value of the feature element
           */
          @Deprecated(since = "10")
          public int major() {
              return feature();
          }
  
          /**
           * Returns the value of the minor element of the version number, or
           * zero if it is absent.
           *
           * @deprecated As of Java&nbsp;SE 10, the second element of a version
           * number is not the minor-release number but the interim-release
           * counter, incremented for every interim release.  Use the {@link
           * #interim()} method in preference to this method.  For compatibility,
           * this method returns the value of the <a href="#INTERIM">interim</a>
           * element, or zero if it is absent.
           *
           * @return The value of the interim element, or zero
           */
          @Deprecated(since = "10")
          public int minor() {
              return interim();
          }
  
          /**
           * Returns the value of the security element of the version number, or
           * zero if it is absent.
           *
           * @deprecated As of Java&nbsp;SE 10, the third element of a version
           * number is not the security level but the update-release counter,
           * incremented for every update release.  Use the {@link #update()}
           * method in preference to this method.  For compatibility, this method
           * returns the value of the <a href="#UPDATE">update</a> element, or
           * zero if it is absent.
           *
           * @return  The value of the update element, or zero
           */
          @Deprecated(since = "10")
          public int security() {
              return update();
          }
  
          /**
           * Returns an unmodifiable {@link java.util.List List} of the integers
           * represented in the <a href="#verNum">version number</a>.
           * The {@code List} always contains at least one element corresponding to
           * the <a href="#FEATURE">feature version number</a>.
           *
           * @return  An unmodifiable list of the integers
           *          represented in the version number
           */
          public List<Integer> version() {
              return version;
          }
  
          /**
           * Returns the optional <a href="#pre">pre-release</a> information.
           *
           * @return  The optional pre-release information as a String
           */
          public Optional<String> pre() {
              return pre;
          }
  
          /**
           * Returns the <a href="#build">build number</a>.
           *
           * @return  The optional build number.
           */
          public Optional<Integer> build() {
              return build;
          }
  
          /**
           * Returns <a href="#opt">optional</a> additional identifying build
           * information.
           *
           * @return  Additional build information as a String
           */
          public Optional<String> optional() {
              return optional;
          }
  
          /**
           * Compares this version to another.
           *
           * <p> Each of the components in the <a href="#verStr">version</a> is
           * compared in the following order of precedence: version numbers,
           * pre-release identifiers, build numbers, optional build information.
           * </p>
           *
           * <p> Comparison begins by examining the sequence of version numbers.
           * If one sequence is shorter than another, then the missing elements
           * of the shorter sequence are considered to be less than the
           * corresponding elements of the longer sequence. </p>
           *
           * <p> A version with a pre-release identifier is always considered to
           * be less than a version without one.  Pre-release identifiers are
           * compared numerically when they consist only of digits, and
           * lexicographically otherwise.  Numeric identifiers are considered to
           * be less than non-numeric identifiers.  </p>
           *
           * <p> A version without a build number is always less than one with a
           * build number; otherwise build numbers are compared numerically. </p>
           *
           * <p> The optional build information is compared lexicographically.
           * During this comparison, a version with optional build information is
           * considered to be greater than a version without one. </p>
           *
           * @param  obj
           *         The object to be compared
           *
           * @return  A negative integer, zero, or a positive integer if this
           *          {@code Version} is less than, equal to, or greater than the
           *          given {@code Version}
           *
           * @throws  NullPointerException
           *          If the given object is {@code null}
           */
          @Override
          public int compareTo(Version obj) {
              return compare(obj, false);
          }
  
          /**
           * Compares this version to another disregarding optional build
           * information.
           *
           * <p> Two versions are compared by examining the version string as
           * described in {@link #compareTo(Version)} with the exception that the
           * optional build information is always ignored. </p>
           *
           * <p> This method provides ordering which is consistent with
           * {@code equalsIgnoreOptional()}. </p>
           *
           * @param  obj
           *         The object to be compared
           *
           * @return  A negative integer, zero, or a positive integer if this
           *          {@code Version} is less than, equal to, or greater than the
           *          given {@code Version}
           *
           * @throws  NullPointerException
           *          If the given object is {@code null}
           */
          public int compareToIgnoreOptional(Version obj) {
              return compare(obj, true);
          }
  
          private int compare(Version obj, boolean ignoreOpt) {
              if (obj == null)
                  throw new NullPointerException();
  
              int ret = compareVersion(obj);
              if (ret != 0)
                  return ret;
  
              ret = comparePre(obj);
              if (ret != 0)
                  return ret;
  
              ret = compareBuild(obj);
              if (ret != 0)
                  return ret;
  
              if (!ignoreOpt)
                  return compareOptional(obj);
  
              return 0;
          }
  
          private int compareVersion(Version obj) {
              int size = version.size();
              int oSize = obj.version().size();
              int min = Math.min(size, oSize);
              for (int i = 0; i < min; i++) {
                  int val = version.get(i);
                  int oVal = obj.version().get(i);
                  if (val != oVal)
                      return val - oVal;
              }
              return size - oSize;
          }
  
          private int comparePre(Version obj) {
              Optional<String> oPre = obj.pre();
              if (!pre.isPresent()) {
                  if (oPre.isPresent())
                      return 1;
              } else {
                  if (!oPre.isPresent())
                      return -1;
                  String val = pre.get();
                  String oVal = oPre.get();
                  if (val.matches("\\d+")) {
                      return (oVal.matches("\\d+")
                          ? (new BigInteger(val)).compareTo(new BigInteger(oVal))
                          : -1);
                  } else {
                      return (oVal.matches("\\d+")
                          ? 1
                          : val.compareTo(oVal));
                  }
              }
              return 0;
          }
  
          private int compareBuild(Version obj) {
              Optional<Integer> oBuild = obj.build();
              if (oBuild.isPresent()) {
                  return (build.isPresent()
                          ? build.get().compareTo(oBuild.get())
                          : -1);
              } else if (build.isPresent()) {
                  return 1;
              }
              return 0;
          }
  
          private int compareOptional(Version obj) {
              Optional<String> oOpt = obj.optional();
              if (!optional.isPresent()) {
                  if (oOpt.isPresent())
                      return -1;
              } else {
                  if (!oOpt.isPresent())
                      return 1;
                  return optional.get().compareTo(oOpt.get());
              }
              return 0;
          }
  
          /**
           * Returns a string representation of this version.
           *
           * @return  The version string
           */
          @Override
          public String toString() {
              StringBuilder sb
                  = new StringBuilder(version.stream()
                      .map(Object::toString)
                      .collect(Collectors.joining(".")));
  
              pre.ifPresent(v -> sb.append("-").append(v));
  
              if (build.isPresent()) {
                  sb.append("+").append(build.get());
                  if (optional.isPresent())
                      sb.append("-").append(optional.get());
              } else {
                  if (optional.isPresent()) {
                      sb.append(pre.isPresent() ? "-" : "+-");
                      sb.append(optional.get());
                  }
              }
  
              return sb.toString();
          }
  
          /**
           * Determines whether this {@code Version} is equal to another object.
           *
           * <p> Two {@code Version}s are equal if and only if they represent the
           * same version string.
           *
           * @param  obj
           *         The object to which this {@code Version} is to be compared
           *
           * @return  {@code true} if, and only if, the given object is a {@code
           *          Version} that is identical to this {@code Version}
           *
           */
          @Override
          public boolean equals(Object obj) {
              boolean ret = equalsIgnoreOptional(obj);
              if (!ret)
                  return false;
  
              Version that = (Version)obj;
              return (this.optional().equals(that.optional()));
          }
  
          /**
           * Determines whether this {@code Version} is equal to another
           * disregarding optional build information.
           *
           * <p> Two {@code Version}s are equal if and only if they represent the
           * same version string disregarding the optional build information.
           *
           * @param  obj
           *         The object to which this {@code Version} is to be compared
           *
           * @return  {@code true} if, and only if, the given object is a {@code
           *          Version} that is identical to this {@code Version}
           *          ignoring the optional build information
           *
           */
          public boolean equalsIgnoreOptional(Object obj) {
              if (this == obj)
                  return true;
              if (!(obj instanceof Version))
                  return false;
  
              Version that = (Version)obj;
              return (this.version().equals(that.version())
                  && this.pre().equals(that.pre())
                  && this.build().equals(that.build()));
          }
  
          /**
           * Returns the hash code of this version.
           *
           * @return  The hashcode of this version
           */
          @Override
          public int hashCode() {
              int h = 1;
              int p = 17;
  
              h = p * h + version.hashCode();
              h = p * h + pre.hashCode();
              h = p * h + build.hashCode();
              h = p * h + optional.hashCode();
  
              return h;
          }
      }
  
      private static class VersionPattern {
          // $VNUM(-$PRE)?(\+($BUILD)?(\-$OPT)?)?
          // RE limits the format of version strings
          // ([1-9][0-9]*(?:(?:\.0)*\.[1-9][0-9]*)*)(?:-([a-zA-Z0-9]+))?(?:(\+)(0|[1-9][0-9]*)?)?(?:-([-a-zA-Z0-9.]+))?
  
          private static final String VNUM
              = "(?<VNUM>[1-9][0-9]*(?:(?:\\.0)*\\.[1-9][0-9]*)*)";
          private static final String PRE      = "(?:-(?<PRE>[a-zA-Z0-9]+))?";
          private static final String BUILD
              = "(?:(?<PLUS>\\+)(?<BUILD>0|[1-9][0-9]*)?)?";
          private static final String OPT      = "(?:-(?<OPT>[-a-zA-Z0-9.]+))?";
          private static final String VSTR_FORMAT = VNUM + PRE + BUILD + OPT;
  
          static final Pattern VSTR_PATTERN = Pattern.compile(VSTR_FORMAT);
  
          static final String VNUM_GROUP  = "VNUM";
          static final String PRE_GROUP   = "PRE";
          static final String PLUS_GROUP  = "PLUS";
          static final String BUILD_GROUP = "BUILD";
          static final String OPT_GROUP   = "OPT";
      }
  }
  