Java tutorial
//package com.java2s; import android.support.annotation.NonNull; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Main { public static final int VERIFY_SUCCESS = 0; private static final int VERIFY_LENGTH_ERROR = 1; private static final int VERIFY_TYPE_ERROR = 2; public static int verifyPassword(@NonNull String password) { int length = password.length(); if (length < 6 || length > 18) { return VERIFY_LENGTH_ERROR; } String regex = "^\\w+$"; Pattern pattern = Pattern.compile(regex); Matcher matcher = pattern.matcher(password); if (!matcher.matches()) return VERIFY_TYPE_ERROR; return VERIFY_SUCCESS; } }