Java FileOutputStream class

In this tutorial, we will learn about Java FileOutputStream and its methods with the help of examples.

The java.io package's FileOutputStream class can be used to write data (in bytes) to a file.

It inherits the OutputStream abstract class.

Before learning FileOutputStream, make sure you understandJava File.

Create a FileOutputStream

To create a file output stream, we must first import the java.io.FileOutputStream package. After importing the package, we can use Java to create a file output stream.

1Using the file path

//With boolean parameter
FileOutputStream output = new FileOutputStream(String path, boolean value);
//Without boolean parameter
FileOutputStream output = new FileOutputStream(String path);

Here, we create an output stream that will be linked to the specified file path.

Additionally, the value is an optional boolean parameter. If it is set to true, new data will be appended to the end of the existing data in the file. Otherwise, new data will overwrite the existing data in the file.

2Using the file object

FileOutputStream output = new FileOutputStream(File fileObject);

Here, we create an output stream that will be linked to the file specified by fileObject.

FileOutputStream methods

The FileOutputStream class provides implementations for different methods that appear in the OutputStream class.

write() method

• write() - Write a single byte to the byte file output stream

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

• write(byte[] array, int start, int length)-Write an equal number of bytes from the start position to the array's output stream

Example: Writing data to a file using FileOutputStream

import java.io.FileOutputStream;
public class Main {
　　　　public static void main(String[] args) {
　　　　　　　　
　　　　　　　　String data = "This is a line of text in the file.";
　　　　　　　　try {
　　　　　　　　　　　　FileOutputStream output = new FileOutputStream("output.txt");
　　　　　　　　　　　　byte[] array = data.getBytes();
　　　　　　　　　　　　//Write bytes to the file
　　　　　　　　　　　　output.write(array);
　　　　　　　　　　　　output.close();
　　　　　　　　}
　　　　　　　　catch(Exception e) {
　　　　　　　　　　　　e.getStackTrace();
　　　　　　　　}
　　　　}
}

In the above example, we created a file output stream named output. The file output stream is associated with the fileoutput.txtLink.

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

To write data to the file, we use the write() method.

Here, when we run the program,output.txtThe file will write the following content.

This is a line of text in the file.

Note：The getBytes() method is used in the program to convert a string to a byte array.

flush() method

To clear the output stream, you can use the flush() method. This method forces the output stream to write all data to the target. For example,

import java.io.FileOutputStream;
import java.io.IOException;
public class Main {
　　　　public static void main(String[] args) throws IOException {
　　　　　　　　FileOutputStream out = null;
　　　　　　　　String data = "This is a demonstration of the flush method";
　　　　　　　　try {
　　　　　　　　　　　　out = new FileOutputStream("flush.txt");
　　　　　　　　　　　　//Use the write() method
　　　　　　　　　　　　out.write(data.getBytes());
　　　　　　　　　　　　//Use the flush() method
　　　　　　　　　　　　out.flush();
　　　　　　　　　　　　out.close();
　　　　　　　　}
　　　　　　　　catch(Exception e) {
　　　　　　　　　　　　e.getStackTrace();
　　　　　　　　}
　　　　}
}

When we run the program, the fileflush.txtFilled with text data represented by string

close() Method

To close the file output stream, you can use the close() method. Once this method is called, we cannot use the methods of FileOutputStream.

Other Methods of FileOutputStream