Replace with Java regular expressions and say goodbye to cumbersome string operations

From data to large model application, on November 25th, Hangzhou Yuanchuang Conference was held to share development tips.

In Java programming, we often need to handle string replacement operations. Sometimes, simple string replacement cannot meet our needs, and then we need to use regular expressions to complete more complex string replacement tasks. This article will introduce how to use Java to replace strings based on regular expressions, and illustrate its application scenarios through examples.

1. Overview of regular expressions

Regular expressions, also known as regular expressions, are a logical formula for string operations. They use some predefined specific characters and combinations of these specific characters to form a "regular string". This "regular character" "String" is used to express a filtering logic for strings. It is used to describe and match a series of strings that match a certain syntax rule. It is usually used to retrieve and replace text that matches a certain pattern (rule).

2. How to use Java to replace strings based on regular expressions

There are two ways to replace strings based on regular expressions in Java : one is to use the replaceAll() method of the String class , and the other is to use the Pattern and Matcher classes.

Use the replaceAll() method of the String class

The replaceAll() method is an instance method of the String class, using regular expressions to replace characters in a string. This means we can use more complex patterns to specify which characters to replace. Such as the following code :

// 类名：StringRegexReplacer
// 函数名：replaceWithRegex
// 函数功能：根据正则表达式替换字符串
// POM依赖包：无

import java.util.regex.Pattern;

public class StringRegexReplacer {

    /**
     * 根据正则表达式替换字符串
     * @param inputString 要进行替换的原始字符串
     * @param regex 正则表达式
     * @param replacement 替换后的字符串
     * @return 替换后的结果字符串
     */
    public static String replaceWithRegex(String inputString, String regex, String replacement) {
        // 判断输入参数是否为空
        if (inputString == null || regex == null || replacement == null) {
            throw new IllegalArgumentException("Input strings cannot be null");
        }

        // 使用正则表达式替换字符串
        String replacedString = inputString.replaceAll(regex, replacement);
        
        // 返回替换后的结果字符串
        return replacedString;
    }
}

// 函数示例
// 根据正则表达式替换字符串示例
// 入参：inputString，要进行替换的原始字符串
//       regex，正则表达式
//       replacement，替换后的字符串
// 出参：replacedString，替换后的结果字符串
// 调用示例：
// String inputString = "Hello, 123 World!";
// String regex = "\\d+";
// String replacement = "****";
// String replacedString = StringRegexReplacer.replaceWithRegex(inputString, regex, replacement);
// System.out.println(replacedString);
// 输出结果：例如，将字符串"Hello, 123 World!"中的数字替换为"*"，得到替换后的字符串为："Hello, *** World!"
// 则输出结果为："Hello, *** World!"

Specifically, this code generated by FuncGPT (Hui Function) , launched by the full-stack fully automatic software development tool SoFlu software robot, which focuses on AI- generated Java functions, defines a static method named replaceWithRegex , which receives three Parameters: inputString (original string to be replaced), regex (regular expression), and replacement (replaced string). The method first checks whether the input parameter is empty and throws an exception if it is empty. Then, use inputString.replaceAll(regex, replacement) to perform the replacement operation, and finally return the replaced result string.

In the function example, the code shows how to use this method. For example, replace the numbers in the string "Hello, 123 World!" with "*" , and the replaced string will be: "Hello, *** World!" .

Using the Pattern and Matcher classes

This method is more flexible and can handle complex regular expressions. First, you need to use the Pattern class to compile the regular expression; then, use the Matcher class to match and replace in the target string. The following is a sample code using the Pattern and Matcher classes:

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class RegexReplaceExample {
    public static void main(String[] args) {
        String testString = "This is a test string with numbers: 123, 456, 789";
        String regex = "\\d+"; // 匹配一个或多个数字
        String replacement = "NUM";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(testString);
        String replacedString = matcher.replaceAll(replacement);
        System.out.println(replacedString);
    }
}

Output result: This is a test string with numbers: NUM, NUM, NUM

In this example, we first define a regular expression \\d+ to match one or more numbers. Then, use the compile() method of the Pattern class to compile the regular expression into a Pattern object. Next, use the matches() method of the Matcher class to match in the target string, and use the replaceAll() method to replace the matched string with the specified string. Finally, output the replaced string to the console.

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Replace with Java regular expressions and say goodbye to cumbersome string operations

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