用于字符串内容提取。

import java.util.regex.*;

public class MyDemo {

    public static void main(String[] args) {
        String str = "[img]http://xxxxx.com/xxxx1.jpg[/img]" +
                     "[img]http://xxxxx.com/xxxx2.jpg [/img]" +
                     "[img]http://xxxxx.com/xxxx3.jpg [/img]" +
                     "[img]http://xxxxx.com/xxxx4.jpg [/img]" +
                     "[img]http://xxxxx.com/xxxx5.jpg [/img]" +
                     "[img]http://xxxxx.com/xxxx6.jpg [/img]";
        System.out.println(str.replaceAll("\\[img](.*?)\\[/img]", "$1\n"));
    }
}