Java Scanner nextDouble()

In this guide, you will learn about the Scanner nextDouble() method in Java programming and how to use it with an example.

1. Scanner nextDouble() Method Overview

Definition:

The nextDouble() method of the Scanner class in Java is used to obtain the input as a double. This method parses the next token of the input as a double value.

Syntax:

public double nextDouble()

Parameters:

This method does not take any parameters.

Key Points:

- The method throws InputMismatchException if the next token cannot be translated into a valid double value.

- If the translation is successful, the scanner advances past the input that matched.

- One needs to be cautious when mixing nextDouble() with other next...() methods, especially nextLine(), as they may not consume the entire line, potentially leaving a newline character in the buffer.

2. Scanner nextDouble() Method Example

import java.util.Scanner;

public class ScannerExample {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("Enter a double value:");
        double value = scanner.nextDouble();

        System.out.println("Double the entered value is: " + (value * 2));
    }
}

Output:

Enter a double value:
12.5
Double the entered value is: 25.0

Explanation:

In the provided example, we have instantiated an object of the Scanner class. 

We then use the nextDouble() method to read a double value from the user. 

The program then prints out the double of the entered value. As can be seen, this method reads and processes the input as a double until it encounters a non-double value or a newline.