Scanner nextDouble() method in Java with Examples

12 Oct, 2018
The nextDouble() method of java.util.Scanner class scans the next token of the input as a Double. If the translation is successful, the scanner advances past the input that matched.
Syntax:
public double nextDouble()
Parameters: The function does not accepts any parameter.
Return Value: This function returns the Double scanned from the input.
Exceptions: The function throws three exceptions as described below:
InputMismatchException: if the next token does not matches the Double regular expression, or is out of range
NoSuchElementException: throws if input is exhausted
IllegalStateException: throws if this scanner is closed
Below programs illustrate the above function:
Program 1:
// Java program to illustrate the// nextDouble() method of Scanner class in Java// without parameter  import java.util.*;  public class GFG1 {    public static void main(String[] argv)        throws Exception    {          String s = "Gfg 9 + 6 = 12.0";          // create a new scanner        // with the specified String Object        Scanner scanner = new Scanner(s);          while (scanner.hasNext()) {              // if the next is a Double,            // print found and the Double            if (scanner.hasNextDouble()) {                System.out.println("Found Double value :"                                   + scanner.nextDouble());            }              // if no Double is found,            // print "Not Found:" and the token            else {                System.out.println("Not found Double() value :"                                   + scanner.next());            }        }        scanner.close();    }}
Not found Double() value :Gfg
Found Double value :9.0
Not found Double() value :+
Found Double value :6.0
Not found Double() value :=
Found Double value :12.0

Program 2: To demonstrate InputMismatchException
// Java program to illustrate the// nextDouble() method of Scanner class in Java// InputMismatchException  import java.util.*;  public class GFG1 {    public static void main(String[] argv)        throws Exception    {          try {              String s = "Gfg 9 + 6 = 12.0";              // create a new scanner            // with the specified String Object            Scanner scanner = new Scanner(s);              while (scanner.hasNext()) {                  // if the next is a Double                // print found and the Double                // since the value 60 is out of range                // it throws an exception                  System.out.println("Next Double value :"                                   + scanner.nextDouble());            }            scanner.close();        }        catch (Exception e) {            System.out.println("Exception thrown: " + e);        }    }}
Exception thrown: java.util.InputMismatchException

Program 3: To demonstrate NoSuchElementException
// Java program to illustrate the// nextDouble() method of Scanner class in Java// NoSuchElementException  import java.util.*;  public class GFG1 {    public static void main(String[] argv)        throws Exception    {          try {              String s = "Gfg";              // create a new scanner            // with the specified String Object            Scanner scanner = new Scanner(s);              // Trying to get the next Double value            // more times than the scanner            // Hence it will throw exception            for (int i = 0; i < 5; i++) {                  // if the next is a Double,                // print found and the Double                if (scanner.hasNextDouble()) {                    System.out.println("Found Double value :"                                       + scanner.nextDouble());                }                  // if no Double is found,                // print "Not Found:" and the token                else {                    System.out.println("Not found Double value :"                                       + scanner.next());                }            }            scanner.close();        }        catch (Exception e) {            System.out.println("Exception thrown: " + e);        }    }}
Not found Double value :Gfg
Exception thrown: java.util.NoSuchElementException

Program 4: To demonstrate IllegalStateException
// Java program to illustrate the// nextDouble() method of Scanner class in Java// IllegalStateException  import java.util.*;  public class GFG1 {    public static void main(String[] argv)        throws Exception    {          try {              String s = "Gfg 9 + 6 = 12.0";              // create a new scanner            // with the specified String Object            Scanner scanner = new Scanner(s);              // close the scanner            scanner.close();            System.out.println("Scanner Closed");              System.out.println("Trying to get "                               + "next Double value");              while (scanner.hasNext()) {                  // if the next is a Double,                // print found and the Double                if (scanner.hasNextDouble()) {                    System.out.println("Found Double value :"                                       + scanner.nextDouble());                }                  // if no Double is found,                // print "Not Found:" and the token                else {                    System.out.println("Not found Double value :"                                       + scanner.next());                }            }        }        catch (Exception e) {            System.out.println("Exception thrown: " + e);        }    }}
Scanner Closed
Trying to get next Double value
Exception thrown: java.lang.IllegalStateException: Scanner closed

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#nextDouble()
Java - util package
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