Java Scanner nextDouble()

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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.