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Validate [{"n":1,"q":"What is the purpose of the volatile keyword in Java?","c":["Ensures thread-safe visibility of variables","Prevents a variable from being optimized by the compiler","Locks the variable for exclusive access by a thread","Both Ensures thread-safe visibility of variables and Prevents a variable from being optimized by the compiler"],"a":"Both Ensures thread-safe visibility of variables and Prevents a variable from being optimized by the compiler"},{"n":2,"q":"Which of the following methods in the java.lang.Thread class allows a thread to pause its execution for a specified period?","c":["sleep(long millis)","wait(long millis)","yield()","interrupt()"],"a":"sleep(long millis)"},{"n":3,"q":"In Java, what does the transient keyword do when applied to a field?","c":["Prevents the field from being serialized","Makes the field constant","Makes the field visible only within the current class","Enforces immutability for the field"],"a":"Prevents the field from being serialized"},{"n":4,"q":"Which of the following is true about the hashCode() method in Java?","c":["It must return the same value for equal objects during different executions","It is used by collections like HashMap for determining object equality","It can be overridden to return any integer value","None of the above"],"a":"It must return the same value for equal objects during different executions"},{"n":5,"q":"Which of the following best describes the concept of 'autoboxing' in Java?","c":["The automatic conversion of primitive types to their corresponding wrapper class objects","The automatic conversion of wrapper class objects to their corresponding primitive types","The automatic conversion of primitive types to arrays","The automatic creation of primitive types based on the object class"],"a":"The automatic conversion of primitive types to their corresponding wrapper class objects"},{"n":6,"q":"What will the following code output? System.out.println(10/0);","c":["Infinity","NaN","ArithmeticException","NullPointerException"],"a":"ArithmeticException"},{"n":7,"q":"Which of the following methods can be used to create a synchronized block in Java?","c":["synchronized()","synchronized(this)","synchronized block()","None of the above"],"a":"synchronized(this)"},{"n":8,"q":"What is the default value of a boolean variable in Java?","c":["true","false","null","0"],"a":"false"},{"n":9,"q":"Which of the following interfaces is used for implementing a thread pool in Java?","c":["Executor","Runnable","Callable","ThreadPoolExecutor"],"a":"Executor"},{"n":10,"q":"What is the output of the following code snippet? int[] arr = {1, 2, 3}; System.out.println(arr.getClass());","c":["[I","int[]","[Ljava.lang.Integer;","null"],"a":"[I"},{"n":11,"q":"Which of the following methods is used to prevent a thread from executing?","c":["stop()","interrupt()","yield()","sleep()"],"a":"interrupt()"},{"n":12,"q":"In Java, what does the final keyword do when applied to a class?","c":["Prevents the class from being subclassed","Prevents any method within the class from being overridden","Prevents any field within the class from being modified","None of the above"],"a":"Prevents the class from being subclassed"},{"n":13,"q":"Which Java collection interface defines methods to allow elements to be stored in key-value pairs?","c":["Map","Set","List","Queue"],"a":"Map"},{"n":14,"q":"Which of the following correctly initializes an array of String in Java?","c":["String[] arr = new String[5];","String[] arr = new String[]{};","String arr[] = new String[5];","All of the above"],"a":"All of the above"},{"n":15,"q":"In Java, which method must be implemented when a class implements the Runnable interface?","c":["run()","start()","execute()","main()"],"a":"run()"},{"n":16,"q":"What is the output of the following code? System.out.println(1 + 2 + "3" + 4);","c":["1234","7","12","34"],"a":"1234"},{"n":17,"q":"Which of the following classes in Java are used for reading character data from a file?","c":["FileReader","BufferedReader","FileInputStream","ByteArrayInputStream"],"a":"FileReader"},{"n":18,"q":"What is the default initial capacity of an ArrayList in Java?","c":["10","5","15","20"],"a":"10"},{"n":19,"q":"Which exception is thrown when an attempt is made to divide by zero in Java?","c":["ArithmeticException","ZeroDivisionException","IllegalArgumentException","MathException"],"a":"ArithmeticException"},{"n":20,"q":"Which of the following statements is true about Java's garbage collection process?","c":["It frees memory by reclaiming unused objects","It runs only when the heap memory is full","It must be explicitly triggered by the programmer","It can only be triggered by system calls"],"a":"It frees memory by reclaiming unused objects"},{"n":21,"q":"Which of the following is true about the java.lang.Object class in Java?","c":["Every class in Java implicitly inherits from Object","The Object class is a subclass of all other classes","Only interfaces inherit from the Object class","The Object class has no methods"],"a":"Every class in Java implicitly inherits from Object"},{"n":22,"q":"Which method is used to serialize an object in Java?","c":["writeObject()","serialize()","saveObject()","toByteArray()"],"a":"writeObject()"},{"n":23,"q":"In Java, which of the following is a valid way to declare a generic method?","c":["public <T> void method(T t)","public void method<T>(T t)","public void method(T t)<T>","public <T> method(T t)"],"a":"public <T> void method(T t)"},{"n":24,"q":"Which class in Java is used for reading binary data from a file?","c":["FileInputStream","ObjectInputStream","DataInputStream","BufferedInputStream"],"a":"FileInputStream"},{"n":25,"q":"In Java, which keyword is used to invoke a constructor of the parent class?","c":["super","this","parent","base"],"a":"super"},{"n":26,"q":"Which method is used by Java collections like ArrayList and HashMap to check if an object contains an element?","c":["contains()","exists()","has()","includes()"],"a":"contains()"},{"n":27,"q":"Which Java keyword is used to prevent the inheritance of a class?","c":["final","abstract","static","private"],"a":"final"},{"n":28,"q":"What is the output of the following code? System.out.println(5/2.0);","c":["2","2.0","2.5","3"],"a":"2.5"},{"n":29,"q":"In Java, which of the following is not a valid way to create an anonymous class?","c":["new MyClass() { ... }","new MyClass() {...};","new MyClass() { public void method() {...} }","new MyClass() {};"],"a":"new MyClass() {...};"},{"n":30,"q":"Which class does the HashMap class implement in Java?","c":["Map","Set","List","Queue"],"a":"Map"},{"n":31,"q":"What does the static keyword mean when applied to a method in Java?","c":["The method can only be accessed from within the class","The method belongs to the class rather than instances of the class","The method can be inherited by subclasses","The method can only be invoked from static contexts"],"a":"The method belongs to the class rather than instances of the class"},{"n":32,"q":"Which of the following statements is true about Java interfaces?","c":["An interface can contain method implementations","A class can implement multiple interfaces","An interface can extend multiple classes","A class can implement only one interface"],"a":"A class can implement multiple interfaces"},{"n":33,"q":"Which of the following methods is used to sort an array in Java?","c":["sort()","arraySort()","Arrays.sort()","Array.sort()"],"a":"Arrays.sort()"},{"n":34,"q":"Which of the following is a correct statement about Java's exception handling mechanism?","c":["Exceptions are mandatory in Java","Unchecked exceptions must be handled with try-catch blocks","Checked exceptions must be either caught or declared in the method signature","Only runtime exceptions can be caught"],"a":"Checked exceptions must be either caught or declared in the method signature"},{"n":35,"q":"What is the default value of a String in Java when it is declared but not initialized?","c":["null","empty string","undefined","0"],"a":"null"},{"n":36,"q":"Which class is used to perform low-level I/O operations in Java?","c":["FileInputStream","BufferedReader","ObjectInputStream","DataOutputStream"],"a":"FileInputStream"},{"n":37,"q":"Which of the following Java constructs provides a way to ensure that resources are automatically closed after use?","c":["try-with-resources","finally block","exception handlers","None of the above"],"a":"try-with-resources"},{"n":38,"q":"Which of the following exceptions is thrown when you try to access an array index that is out of bounds in Java?","c":["ArrayIndexOutOfBoundsException","IndexOutOfRangeException","OutOfBoundsException","InvalidIndexException"],"a":"ArrayIndexOutOfBoundsException"},{"n":39,"q":"Which of the following is not a valid way to handle exceptions in Java?","c":["try-catch-finally","throws clause","throw statement","do-while"],"a":"do-while"},{"n":40,"q":"In Java, which of the following is true about the instanceof operator?","c":["It checks if an object is an instance of a class or interface","It can only be used with classes, not interfaces","It checks whether two classes are equal","It cannot be used on generic types"],"a":"It checks if an object is an instance of a class or interface"}] q - question c - choices a - answer