Java IO Tutorial - Java PushbackInputStream

A PushbackInputStream adds functionality to an input stream allowing us to push back the read bytes using its unread() method.

There are three versions of the unread() method. One lets us push back one byte and other two let us push back multiple bytes.

Example

import java.io.FileInputStream;
import java.io.PushbackInputStream;
/*from www .jav a  2 s .c  o m*/
public class Main {
  public static void main(String[] args) {
    String srcFile = "test.txt";

    try (PushbackInputStream pis = new PushbackInputStream(new FileInputStream(
        srcFile))) {
      byte byteData;
      while ((byteData = (byte) pis.read()) != -1) {
        System.out.print((char) byteData);
        pis.unread(byteData);
        // Reread the byte we unread
        byteData = (byte) pis.read();
        System.out.print((char) byteData);
      }
    } catch (Exception e2) {
      e2.printStackTrace();
    }
  }
}

The code above generates the following result.