Java - DataOutputStream write(byte[] b, int off, int len)

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Description

The Java DataOutputStream write(byte[] b, int off, int len) method writes len bytes from the specified byte array b starting at position off to the underlying output stream.

Declaration

Following is the declaration for java.io.DataOutputStream.write(byte[] b, int off, int len) method −

public void write(byte[] b, int off, int len)

Parameters

• b − The source buffer.

• off − The start position off.

• len − The number of bytes to write to the stream.

Return Value

This method does not return any value.

Exception

IOException − If an I/O error occurs.

Example 1

The following example shows the usage of Java DataOutputStream write(byte[] b, int off, int len) method. We've created ByteArrayOutputStream and DataOutputStream reference. A byte[] buf is initialized with some byte values. A ByteArrayOutputStream object is created. Then DataOutputStream is initialized with ByteArrayOutputStream object created before. Then a part of byte array is written to dataoutputstream. As next step, stream is flushed using flush() method and ByteArrayOutputStream is iterated to print the bytes written to the stream. Finally we're closing all the streams.

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
public class DataOutputStreamDemo {
   public static void main(String[] args) throws IOException {
      ByteArrayOutputStream baos = null;
      DataOutputStream dos = null;
      byte[] buf = {87,64,72,31,90};
      
      try {
         // create byte array output stream
         baos = new ByteArrayOutputStream();
         
         // create data output stream
         dos = new DataOutputStream(baos);
         
         // write to the stream from the source buffer
         dos.write(buf, 2, 3);
         
         // flushes bytes to underlying output stream
         dos.flush();
   
         // for each byte in the baos buffer content
         for(byte b:baos.toByteArray()) {
            System.out.println(b);
         }         
      } catch(Exception e) {
         // if any error occurs
         e.printStackTrace();
      } finally {
         
         // releases all system resources from the streams
         if(dos!=null)
            dos.close();
         if(baos!=null)
            baos.close();
      }
   }
}

Output

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

72
31
90

Example 2

The following example shows the usage of Java DataOutputStream write(byte[] b, int off, int len) method. We've created ByteArrayOutputStream and DataOutputStream reference. A byte[] buf is initialized with some byte values. A ByteArrayOutputStream object is created. Then DataOutputStream is initialized with ByteArrayOutputStream object created before. Then complete byte array is written to dataoutputstream by passing index as 0 and length of byte array. As next step, stream is flushed using flush() method and ByteArrayOutputStream is iterated to print the bytes written to the stream. Finally we're closing all the streams.

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
public class DataOutputStreamDemo {
   public static void main(String[] args) throws IOException {
      ByteArrayOutputStream baos = null;
      DataOutputStream dos = null;
      byte[] buf = {87,64,72,31,90};
      
      try {
         // create byte array output stream
         baos = new ByteArrayOutputStream();
         
         // create data output stream
         dos = new DataOutputStream(baos);
         
         // write to the stream from the source buffer
         dos.write(buf, 0, buf.length);
         
         // flushes bytes to underlying output stream
         dos.flush();
   
         // for each byte in the baos buffer content
         for(byte b:baos.toByteArray()) {
            System.out.println(b);
         }
         
      } catch(Exception e) {
         // if any error occurs
         e.printStackTrace();
      } finally {
         // releases all system resources from the streams
         if(dos!=null)
            dos.close();
         if(baos!=null)
            baos.close();
      }
   }
}

Output

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

87
64
72
31
90