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Java Scanner nextBoolean() Method
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
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