Java String with only ASCII letter and digit
//package com.demo2s; public class Main { public static void main(String[] argv) throws Exception { String s = "demo2s.com"; int m = 2; int n = 2; System.out.println(allAlphaNum(s, m, n)); }//from w w w .j av a 2 s . c o m public static boolean allAlphaNum(String s, int m, int n) { for (int i = m; i < n; i++) if (!isAlpha(s.charAt(i)) && !isDigit(s.charAt(i))) return false; return true; } public static boolean isAlpha(int c) { return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'); } public static boolean isDigit(int c) { return '0' <= c && c <= '9'; } }