Scanner nextBoolean() in Java

nextBoolean(): This method is available in java.util.Scanner class of Java.

Syntax:

boolean java.util.Scanner.nextBoolean()

This method scans the next token of the input into a boolean value and returns that value.

Parameters: NA

Returns: the boolean scanned from the input.

Throws:

1. InputMismatchException - if the next token is not a valid boolean.

2. NoSuchElementException - if input is exhausted.

3. IllegalStateException - if this scanner is closed

Approach 1: When no exception

Java

import java.util.Scanner;

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

        String source = "true Hello World";
        Scanner scanner = new Scanner(source);

        System.out.println(scanner.nextBoolean());

        scanner.close();
    }
}

Output:

true

Approach 2: InputMismatchException 

Java

import java.util.Scanner;

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

        String source = "Hello World";
        Scanner scanner = new Scanner(source);

        System.out.println(scanner.nextBoolean());

        scanner.close();
    }
}

Output:

Exception in thread "main" java.util.InputMismatchException
	at java.base/java.util.Scanner.throwFor(Scanner.java:939)
	at java.base/java.util.Scanner.next(Scanner.java:1594)
	at java.base/java.util.Scanner.nextBoolean(Scanner.java:1893)
	

Approach 3: NoSuchElementException

Java

import java.util.Scanner;

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

        String source = "";
        Scanner scanner = new Scanner(source);

        System.out.println(scanner.nextBoolean());

        scanner.close();
    }
}

Output:

Exception in thread "main" java.util.NoSuchElementException
	at java.base/java.util.Scanner.throwFor(Scanner.java:937)
	at java.base/java.util.Scanner.next(Scanner.java:1594)
	at java.base/java.util.Scanner.nextBoolean(Scanner.java:1893)
	

Approach 4: IllegalStateException

Java

import java.util.Scanner;

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

        String source = "true Hello World";
        Scanner scanner = new Scanner(source);

        scanner.close();
        System.out.println(scanner.nextBoolean());

    }
}

Output:

Exception in thread "main" java.lang.IllegalStateException: Scanner closed
	at java.base/java.util.Scanner.ensureOpen(Scanner.java:1150)
	at java.base/java.util.Scanner.next(Scanner.java:1573)
	at java.base/java.util.Scanner.nextBoolean(Scanner.java:1893)