Java经典实例：正则表达式，找到匹配的文本

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

/**
 * Created by Frank
 */
public class REMatch {
    public static void main(String[] args) {
        String patt = "Q[^u]\d+\.";
        Pattern r = Pattern.compile(patt);
        String line = "Order QT300. Now! QT400.";
        Matcher m = r.matcher(line);
        int i = 0;
        while (m.find()) {
            // group(0)或group()将会返回整个匹配的字符串（完全匹配）；group(i)则会返回与分组i匹配的字符
            // 这个例子只有一个分组
            System.out.println(patt + " matches "" + m.group(0) + "" in "" + line + """);
            System.out.println("start:" + m.start() + " end:" + m.end());
        }
    }
}

输出：

Q[^u]d+. matches "QT300." in "Order QT300. Now! QT400."
start:6 end:12
Q[^u]d+. matches "QT400." in "Order QT300. Now! QT400."
start:18 end:24

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

/**
 * Created by Frank
 */
public class REMatchTwoFields {
    public static void main(String[] args) {
        String inputLine = "Adams,John Quincy";
        Pattern r = Pattern.compile("(.*),(.*)");
        Matcher m = r.matcher(inputLine);
        if (!m.matches()) {
            throw new IllegalArgumentException("Bad Input");
        }
        // 分组0得到的是整个原字符串
        for (int i = 0; i < m.groupCount() + 1; i++) {
            System.out.println("分组" + i + ":" + m.group(i));
        }
    }
}

输出：

分组0:Adams,John Quincy
分组1:Adams
分组2:John Quincy