关于java的RegularExperssion报错的问题

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

/**
 * @author lingchen
 *
 */
public class RegExpTest2 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        String str = "<div>zhangsan</div>";
        Pattern p = Pattern.compile("(?<=<(\\w+)>)(.*)(?=</\\1>)");
        Matcher m = p.matcher(str);
        while (m.find()) {
            System.out.println(m.group());
        }

    }
}

 Exception in thread "main" java.util.regex.PatternSyntaxException: Look-behind group does not have an obvious maximum length near index 10
(?<=<(\w+)>)(.*)(?=</\1>)
          ^
    at java.util.regex.Pattern.error(Pattern.java:1924)
    at java.util.regex.Pattern.group0(Pattern.java:2812)
    at java.util.regex.Pattern.sequence(Pattern.java:2018)
    at java.util.regex.Pattern.expr(Pattern.java:1964)
    at java.util.regex.Pattern.compile(Pattern.java:1665)
    at java.util.regex.Pattern.<init>(Pattern.java:1337)
    at java.util.regex.Pattern.compile(Pattern.java:1022)
    at com.comtop.regexp.RegExpTest2.main(RegExpTest2.java:20)

根据国外的stackoverflow网站上的大神回答，Java的环视表达式中不支持变长式，比如你这里的\w+
只能写成\w{1,3}

有哪儿高手来指点迷津，不胜感激。

大于小于需要转义。你忘记转义了。

正则表达式语法错误