Java tutorial
//package com.java2s; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Main { public static boolean isPassword(String mobiles) { Pattern p = Pattern.compile("^(?![0-9]+$)(?![a-zA-Z]+$)[0-9A-Za-z]{6,20}$"); Matcher m = p.matcher(mobiles); return m.matches(); } }