Java tutorial
//package com.java2s; //License from project: Apache License public class Main { public static String spliteMobile(String mobile) { StringBuffer buffer = new StringBuffer(mobile); char[] chars = buffer.reverse().toString().toCharArray(); StringBuffer result = new StringBuffer(); for (int i = chars.length - 1; i >= 0; i--) { if (i % 4 == 0) { result.append(chars[i]).append(" "); } else { result.append(chars[i]); } } return result.toString(); } }