Scanner hasNextDouble() method in Java with Examples

The hasNextDouble() method of java.util.Scanner class returns true if the next token in this scanner’s input can be interpreted as a Double using the nextDouble() method. The scanner does not advance past any input.

Syntax:

public Double hasNextDouble()

Parameters: The function does not accepts any parameter.

Return Value: This function returns true if and only if this scanner’s next token is a valid Double.

Exceptions: The function throws IllegalStateException if this scanner is closed.

Below programs illustrate the above function:

Program 1:

// Java program to illustrate the
// hasNextDouble() 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 2 geeks!";

        // new scanner with the
        // specified String Object
        Scanner scanner = new Scanner(s);

        // use US locale to interpret Doubles in a string
        scanner.useLocale(Locale.US);

        // iterate till end
        while (scanner.hasNext()) {

            // check if the scanner's
            // next token is a Double with the default radix
            System.out.print("" + scanner.hasNextDouble());

            // print what is scanned
            System.out.print(" -> " + scanner.next() + "\n");
        }

        // close the scanner
        scanner.close();
    }
}

Output:

false -> gfg
true -> 2
false -> geeks!

Program 2: Program to demonstrate exception

// Java program to illustrate the
// hasNextDouble() method of Scanner class in Java
// Exception case

import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {

        try {
            String s = "gfg 2 geeks!";

            // new scanner with the
            // specified String Object
            Scanner scanner = new Scanner(s);

            // use US locale to interpret Doubles in a string
            scanner.useLocale(Locale.US);

            scanner.close();

            // iterate till end
            while (scanner.hasNext()) {

                // check if the scanner's
                // next token is a Double with the default radix
                System.out.print("" + scanner.hasNextDouble());

                // print what is scanned
                System.out.print(" -> " + scanner.next() + "\n");
            }

            // close the scanner
            scanner.close();
        }
        catch (IllegalStateException e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

Exception: java.lang.IllegalStateException: Scanner closed

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#hasNextDouble()