Java OutputStream Class

In this tutorial, we will learn about Java OutputStream and its methods through an example.

The OutputStream class in the java.io package is an abstract superclass that represents a byte output stream.

Since OutputStream is an abstract class, it is not useful by itself. However, its subclasses can be used to write data.

OutputStream Subclasses

To use the features of OutputStream, we can use its subclasses. Some of them are:

• FileOutputStream

• ByteArrayOutputStream

• ObjectOutputStream

In the next tutorial, we will learn about all these subclasses.

Create an OutputStream

To create an OutputStream, we must first import the java.io.OutputStream package. After importing the package, we can create an output stream.

//Create an OutputStream
OutputStream object = new FileOutputStream();

Here, we have created an output stream object FileOutputStream. Since OutputStream is an abstract class, we cannot create an object of OutputStream.

Note: We can also create output streams from other subclasses of the OutputStream class.

OutputStream Methods

The OutputStream class provides various methods implemented by its subclasses. The following are some of them:

• write() - Write the specified bytes into the output stream

• write(byte[] array) - Write the bytes from the specified array into the output stream

• flush() -　 Force all existing data in the output stream to be written to the target

• close() - Close the output stream

Example: Using OutputStream with FileOutputStream

Below is the method implemented by the FileOutputStream class using OutputStream.

import java.io.FileOutputStream;
import java.io.OutputStream;
public class Main {
　　　　public static void main(String args[]) {
　　　　　　　　String data = "This is a line of text within the file.";
　　　　　　　　try {
　　　　　　　　　　　　OutputStream out = new FileOutputStream("output.txt");
　　　　　　　　　　　　//Convert a string to bytes
　　　　　　　　　　　　byte[] dataBytes = data.getBytes();
　　　　　　　　　　　　//Write data to the output stream
　　　　　　　　　　　　out.write(dataBytes);
　　　　　　　　　　　　System.out.println("Data has been written to the file.");
　　　　　　　　　　　　//Close the output stream
　　　　　　　　　　　　out.close();
　　　　　　　　}
　　　　　　　　catch (Exception e) {
　　　　　　　　　　　　e.getStackTrace();
　　　　　　　　}
　　　　}
}

In the above example, we used the FileOutputStream class to create an output stream. Now, the output stream is connected to the fileoutput.txtLink.

OutputStream out = new FileOutputStream("output.txt");

To write data tooutput.txtThe file, we have implemented these methods.

output.write();　　　　　　//Write data to the file
output.close();　　　　　　//Close the output stream

When we run the program,output.txtThe file will be written with the following content.

This is a line of text within the file.