Java Scanner nextBoolean() Method

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Description

The java Scanner nextBoolean() method scans the next token of the input into a boolean value and returns that value. This method will throw InputMismatchException if the next token cannot be translated into a valid boolean value. If the match is successful, the scanner advances past the input that matched.

Declaration

Following is the declaration for java.util.Scanner.nextBoolean() method

public boolean nextBoolean()

Parameters

NA

Return Value

This method returns the boolean scanned from the input

Exception

• InputMismatchException − if the next token is not a valid boolean

• NoSuchElementException − if the input is exhausted

• IllegalStateException − if this scanner is closed

Getting Next Token as Boolean of a Scanner on a String Example

The following example shows the usage of Java Scanner nextBoolean() method to scan the next token as Boolean. We've created a scanner object using a given string. Then we checked each token to be Boolean and printed otherwise Not Found is printed along with scanned token. In the end scanner is closed using close() method.

package com.tutorialspoint;

import java.util.Scanner;

public class ScannerDemo {
   public static void main(String[] args) {

      String s = "Hello World! true 3 + 3.0 = 6";

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

      while (scanner.hasNext()) {
         
         // check if the scanner's next token is a Boolean
         if(scanner.hasNextBoolean()){
            // print what is scanned
            System.out.println("Found: " + scanner.nextBoolean());		 
         } else {
            System.out.println("Not Found: " + scanner.next());
         }
      }

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

Output

Let us compile and run the above program, this will produce the following result −

Not Found: Hello
Not Found: World!
Found: true
Not Found: 3
Not Found: +
Not Found: 3.0
Not Found: =
Not Found: 6

Getting Next Token as Boolean of a Scanner on User Input Example

The following example shows the usage of Java Scanner nextBoolean() method to scan the next token as Boolean. We've created a scanner object using System.in class. Then we checked each token to be Boolean and printed otherwise Not Found is printed along with scanned token. In the end scanner is closed using close() method.

package com.tutorialspoint;

import java.util.Scanner;

public class ScannerDemo {
   public static void main(String[] args) {

      // create a new scanner with System Input
      Scanner scanner = new Scanner(System.in);
         
      while (scanner.hasNext()) {
         
         // check if the scanner's next token is a Boolean
         if(scanner.hasNextBoolean()){
            // print what is scanned
            System.out.println("Found: " + scanner.nextBoolean());		 
         } else {
            System.out.println("Not Found: " + scanner.next());
         }
      }

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

Output

Let us compile and run the above program, this will produce the following result − (where we've entered 3.0.)

true
Found: true

Getting Next Token as Boolean of a Scanner on Properties File Example

The following example shows the usage of Java Scanner nextBoolean() method to scan the next token as Boolean. We've created a scanner object using a file properties.txt. Then we checked each token to be Boolean and printed otherwise Not Found is printed along with scanned token. In the end scanner is closed using close() method.

package com.tutorialspoint;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class ScannerDemo {
   public static void main(String[] args) throws FileNotFoundException {

      // create a new scanner with a file as input
      Scanner scanner = new Scanner(new File("properties.txt"));
         
      while (scanner.hasNext()) {
         
         // check if the scanner's next token is a Boolean
         if(scanner.hasNextBoolean()){
            // print what is scanned
            System.out.println("Found: " + scanner.nextBoolean());		 
         } else {
            System.out.println("Not Found: " + scanner.next());
         }
      }

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

Assuming we have a file properties.txt available in your CLASSPATH, with the following content. This file will be used as an input for our example program −

Hello World! true + false

Output

Let us compile and run the above program, this will produce the following result −

Not Found: Hello
Not Found: World!
Found: true
Not Found: +
Found: false