Java tutorial
import java.io.*; public class Main { public static void main(String[] args) { String s = "from java2s.com"; StringReader sr = new StringReader(s); // create a new PushBack reader based on our string reader PushbackReader pr = new PushbackReader(sr, 20); try { // read the first five chars for (int i = 0; i < 5; i++) { char c = (char) pr.read(); System.out.println(c); } // unread a character pr.unread('F'); // read the next char, which is the one we unread char c = (char) pr.read(); System.out.println(c); pr.close(); } catch (IOException ex) { ex.printStackTrace(); } } }