Java tutorial
//package com.java2s; public class Main { public static boolean isInteger(String s) { return isInteger(s, 10); } public static boolean isInteger(String s, int radix) { if (s.isEmpty()) return false; for (int i = 0; i < s.length(); i++) { if (i == 0 && s.charAt(i) == '-') { if (s.length() == 1) return false; else continue; } if (Character.digit(s.charAt(i), radix) < 0) return false; } return true; } }