Java.io.PushbackInputStream.read() Method

Description

The java.io.PushbackInputStream.read(byte[] b,int off,int len) method reads up to len bytes of data from this input stream into an array of bytes. This method first reads any pushed-back bytes; after that, if fewer than len bytes have been read then it reads from the underlying input stream. If len is not zero, the method blocks until at least 1 byte of input is available; otherwise, no bytes are read and 0 is returned.

Declaration

Following is the declaration for java.io.PushbackInputStream.read() method.

public int read(byte[] b,int off,int len)

Parameters

• b − The buffer into which the data is read.

• off − The start offset in the destination array b.

• len − The maximum number of bytes read.

Return Value

This method returns the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.

Exception

• NullPointerException − If b is null.

• IndexOutOfBoundsException − If off is negative, len is negative, or len is greater than b.length - off.

• IOException − If this input stream has been closed by invoking its close() method, or an I/O error occurs.

Example

The following example shows the usage of java.io.PushbackInputStream.read() method.

package com.tutorialspoint;

import java.io.*;

public class PushbackInputStreamDemo {
   public static void main(String[] args) {

      // declare a buffer and initialize its size:
      byte[] arrByte = new byte[1024];

      // create an array for our message
      byte[] byteArray = new byte[]{'H', 'e', 'l', 'l', 'o'};

      // create object of PushbackInputStream class for specified stream
      InputStream is = new ByteArrayInputStream(byteArray);
      PushbackInputStream pis = new PushbackInputStream(is);

      try {
         // read a char into our array
         pis.read(arrByte, 0, 3);

         // print arrByte
         for (int i = 0; i < 3; i++) {
            System.out.print((char) arrByte[i]);
         }
      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
}

Let us compile and run the above program, this will produce the following result −

Hel