Apache Commons IO - TeeInputStream Class

Overview

TeeInputStream class is an InputStream proxy that transparently writes a copy of all bytes which are read from the proxy stream to a given OutputStream. The proxy input stream is closed, when the close() method on this proxy is called. It can be used to operate two streams collectively at a time.

Class Declaration

Following is the declaration for org.apache.commons.io.input.TeeInputStream Class −

public class TeeInputStream
   extends ProxyInputStream

Steps of Using TeeInputStream

Step 1: Create a TeeOutputStream for two outputstreams

// create two output streams
ByteArrayOutputStream outputStream1 = new ByteArrayOutputStream();
ByteArrayOutputStream outputStream2 = new ByteArrayOutputStream();
TeeOutputStream teeOutputStream = new TeeOutputStream(outputStream1, outputStream2);

Step 2: Create a TeeInputStream for TeeOutputStream

// create an input stream
ByteArrayInputStream inputStream = new ByteArrayInputStream("data".getBytes("US-ASCII"));
// create teeInputStream using inputStream, teeOutputStream and closeBranch flag as true
// if closeBranch is true, outputstream is automatically closed when teeInputstream is closed.
TeeInputStream teeInputStream = new TeeInputStream(inputStream, teeOutputStream, true);
Step 3: Read Data using TeeInputStream
teeInputStream.read(new byte["data".length()]);
Step 4: Verify data in output streams
System.out.println("Output stream 1: " + outputStream1.toString());
System.out.println("Output stream 2: " + outputStream2.toString());
Step 5: Close the stream.
//teeIn.close() closes teeIn and teeOut which in turn closes the out1 and out2.
teeInputStream.close();

Example - Usage of TeeInputStream.
CommonsIoTester.java
package com.tutorialspoint;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import org.apache.commons.io.input.TeeInputStream;
import org.apache.commons.io.output.TeeOutputStream;

public class CommonsIoTester {
   private static final String SAMPLE = "Welcome to TutorialsPoint. Simply Easy Learning.";
   public static void main(String[] args) {
      try {
         usingTeeInputStream();
      }catch(IOException e) {
         System.out.println(e.getMessage());
      }
   }
   public static void usingTeeInputStream() throws IOException {
      TeeInputStream teeInputStream = null;
      TeeOutputStream teeOutputStream = null;
      try {
         ByteArrayInputStream inputStream = new
         ByteArrayInputStream(SAMPLE.getBytes("US-ASCII"));
         ByteArrayOutputStream outputStream1 = new ByteArrayOutputStream();
         ByteArrayOutputStream outputStream2 = new ByteArrayOutputStream();
         teeOutputStream = new TeeOutputStream(outputStream1, outputStream2);
         teeInputStream = new TeeInputStream(inputStream, teeOutputStream, true);
         teeInputStream.read(new byte[SAMPLE.length()]);
         System.out.println("Output stream 1: " + outputStream1.toString());
         System.out.println("Output stream 2: " + outputStream2.toString());
      }catch (IOException e) {
         System.out.println(e.getMessage());
      } finally {
         //teeIn.close() closes teeIn and teeOut which in turn closes the out1 and out2.
         try {
            teeInputStream.close();
         } catch (IOException e) {
            System.out.println(e.getMessage());
         }
      }
   }
}

Output
It will print the following result −
Output stream 1: Welcome to TutorialsPoint. Simply Easy Learning.
Output stream 2: Welcome to TutorialsPoint. Simply Easy Learning.