Scanner nextDouble() in Java

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

Syntax:

double java.util.Scanner.nextDouble()

This method scans the next token of the input as a double.

Parameters: NA

Returns: the double scanned from the input.

Throws:

1. InputMismatchException - if the next token does not match the Float regular expression, or is out of range.

2. NoSuchElementException - if the input is exhausted.

3. IllegalStateException - if this scanner is closed

Approach 1: When no exception

Java

import java.util.Scanner;

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

        String source = "1661.881 Hello World";
        Scanner scanner = new Scanner(source);

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

        scanner.close();
    }
}

Output:

1661.881

Approach 2: InputMismatchException 

Java

import java.util.Scanner;

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

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

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

        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.nextDouble(Scanner.java:2564)
	

Approach 3: NoSuchElementException

Java

import java.util.Scanner;

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

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

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

        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.nextDouble(Scanner.java:2564)
	

Approach 4: IllegalStateException 

Java

import java.util.Scanner;

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

        String source = "1717.191 Hello World";
        Scanner scanner = new Scanner(source);

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

    }
}

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.nextDouble(Scanner.java:2564)