Interpretation of Java documentation: Functional analysis of the parseDouble() method of the Double class

Java Document Interpretation: Function analysis of the parseDouble() method of the Double class requires specific code examples

In Java development, it is often necessary to perform string type numbers Convert to double type. In Java, the parseDouble() method of the Double class provides us with a convenient and reliable method to convert a string into a double type. This article will introduce in detail the function and usage of the parseDouble() method of the Double class.

Introduction to the parseDouble() method of the Double class

First, let’s take a look at the definition of the parseDouble() method of the Double class:

public static double parseDouble(String s) throws NumberFormatException{}

As can be seen from the above definition, the parseDouble() method is a static method that accepts a string type parameter s as input, which represents a number to be converted to a double type. String. If the string s cannot be converted to type double, this method will throw a NumberFormatException.

Function of the parseDouble() method of the Double class

The main function of the parseDouble() method of the Double class is to parse string type numbers into double type values. The parsing process follows the syntax in the Java Language Specification, including the following situations:

1. Number strings with positive and negative signs

For digital characters with positive and negative signs String, parseDouble() method can parse correctly, for example:

double d1 = Double.parseDouble("123.45"); // Return: 123.45
double d2 = Double.parseDouble("-56.78") ; // Return: -56.78

2. Floating point string

For floating point strings, the parseDouble() method can also be parsed correctly, for example:

double d3 = Double.parseDouble("1.23456"); // Returns: 1.23456
double d4 = Double.parseDouble("-6.789e-2"); // Returns: -0.06789

3. Non-numeric string

If the input string cannot be parsed into a double value, the parseDouble() method will throw a NumberFormatException, for example:

double d5 = Double.parseDouble("abc"); // Throws a NumberFormatException

How to use the parseDouble() method of the Double class

Let's take a look at the parseDouble() method of the Double class The specific use of the method. Suppose we have a string type numeric string s. To convert it to a double type value, you can use the following code:

try {

double d = Double.parseDouble(s);
// 数字字符串s被成功转换为double类型的数值d

} catch (NumberFormatException e) {

// 字符串s不能被转换为double类型的数值，抛出NumberFormatException异常

}

It should be noted that since the parseDouble() method may throw a NumberFormatException exception, it is best to put it in a try-catch code block when using it to avoid the program in Crash when an exception occurs.

Sample code of the parseDouble() method of the Double class

The following is a sample code using the parseDouble() method of the Double class, which reads the string type entered by the user from the console number, convert it to a double type value, and calculate its square value:

import java.util.Scanner;

public class ParseDoubleExample {

public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.print("请输入一个数字：");
    String s = scanner.nextLine();
    try {
        double d = Double.parseDouble(s);
        System.out.println("输入的数字为：" + d);
        System.out.println("该数字的平方为：" + d * d);
    } catch (NumberFormatException e) {
        System.out.println("输入的字符串"" + s + ""不能被转换为数字。");
    }
    scanner.close();
}

}

Run the above code, the execution effect is as follows:

Please enter a number: 12.345
The entered number is: 12.345
The square of the number is: 152.39902499999998

Summary

In this article, we have a detailed introduction to the parseDouble() method of the Double class in Java, including its functions, usage and sample code. This method provides Java developers with a convenient and reliable method to convert string type numbers into double type values. In actual development, you can use the parseDouble() method to complete the string conversion function as needed.

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