Java PushbackReader.unread(int c)

public void unread(int c)  throws IOException

/* w w w  .  j av a 2 s  .  c om*/

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();
      }
   }
}