Scanner nextDouble() method in Java with Examples

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:

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// 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();
    }
}

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Output:

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

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// 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);
        }
    }
}

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Output:

Exception thrown: java.util.InputMismatchException

Program 3: To demonstrate NoSuchElementException

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// 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);
        }
    }
}

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Output:

Not found Double value :Gfg
Exception thrown: java.util.NoSuchElementException

Program 4: To demonstrate IllegalStateException

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// 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);
        }
    }
}

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Output:

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()



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