java中获取字符串之间的内容

public String getParm(String before,String after,String s){
String matchRegex = before+"(.*?)"+after;
Pattern p = Pattern.compile(matchRegex);
Matcher m = p.matcher(s);
ArrayList<String> strs = new ArrayList<String>();
       while (m.find()) {
           strs.add(m.group(1));            
       } 
       return strs.get(0);
}