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正则表达式30分钟入门教程

java正则表达式的写法

这是研二思科笔试时遇到的题，以此为例保留java正则套路。

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

/**
 * 提取sip地址的头部
 * 方法：用正则
 * 用例：
 *  1.%22hello%22world%22<sip:10000@172.16.130.42> -->hello%22world
 *  2.%22%22hello%22world%22%22%22haha%22%22%22<sip:10000@172.16.130.42> -->hello%22world%22%22%22haha
 *  3.hello22%world<sip:10000@172.16.130.42> -->hello22%world
 */
public class Solution {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String url = sc.next();
        System.out.println(decode(url));
    }

    static String decode(String url){
        if(url.isEmpty() || url.trim().equals("")){
            return "";
        }
        url = url.trim();
        String regex = "^(%22)*(.+(%22)*[^(%22)]+)(%22)*<sip:\\d+@\\d+\\.\\d+\\.\\d+\\.\\d+>$";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(url);
        if(matcher.find()) {
            return matcher.group(2);
        }
        return "";
    }
}

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