Java documentation interpretation: Usage analysis of nextDouble() method of Scanner class

Interpretation of Java documentation: Usage analysis of nextDouble() method of Scanner class

The Scanner class is a convenient input processing tool class provided in Java, which can help us Read data from standard input, a file, or other input stream. Among them, the nextDouble() method is a method provided by the Scanner class for reading floating point data.

1. Method definition and description
In the Java document, according to the definition and description of the method, we can get the following information:

Method definition: public double nextDouble()
Method description: Scans the next complete token from this scanner's input and interprets it as a double-precision floating point number. The return value is an interpreted floating point number. If the input is illegal or the end of the input source has been reached, an InputMismatchException is thrown.

2. Method usage examples
The following uses specific code examples to demonstrate the use of the nextDouble() method in the Scanner class.

import java.util.Scanner;

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

        System.out.print("请输入一个浮点数：");
        // 使用nextDouble()方法读取浮点数
        double num = scanner.nextDouble();

        System.out.println("您输入的浮点数为：" + num);

        // 关闭Scanner对象
        scanner.close();
    }
}

In the above code, we first create a Scanner object, and then use the nextDouble() method to read a floating point number from the standard input. Next, we output the floating point number we read to the console. Finally, we close the Scanner object.

3. Precautions for using the method
When using the nextDouble() method, you need to pay attention to the following points:

1. nextDouble() method will read the next complete mark , that is, a string consisting of all characters before encountering a space, tab key, or newline character.
2. If the input data is not in a valid floating point format, the nextDouble() method will throw an InputMismatchException exception. Therefore, before using this method, you should first make a legality judgment and use the hasNextDouble() method.
3. After using the Scanner object, its close() method should be called to release resources.

Summary:
This article provides a detailed analysis of the nextDouble() method in the Scanner class and gives specific code examples. By using this method, we can easily read the input floating point data. I hope this article is helpful to your study!

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