Java tutorial
//package com.java2s; public class Main { public static String getOnlyNumerics(String str) { if (str == null) { return null; } StringBuffer strBuff = new StringBuffer(); char c; for (int i = 0; i < str.length(); i++) { c = str.charAt(i); if (Character.isDigit(c)) { strBuff.append(c); } } return strBuff.toString(); } }