Java FileOutputStream Class

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

The FileOutputStream class of the java.io package can be used to write data (in bytes) to the files.

It extends the OutputStream abstract class.

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Before you learn about FileOutputStream, make sure to know about Java Files.

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Make a FileOutputStream

To make a file output stream, we should import the java.io.FileOutputStream package first. When we import the package, here is the means by which we can make a file output stream in Java.

1. Using the path to file

// Including the boolean parameter
FileOutputStream output = new FileOutputStream(String path, boolean value);

// Not including the boolean parameter
FileOutputStream output = new FileOutputStream(String path);

Here, we have made an output stream that will be connected to the file determined by the path.

Likewise, value is a discretionary boolean parameter. If it is set to true, the new data will be affixed to the furthest limit of the current data in the document. Something else, the new information overwrites the current data in the file.

2. Using an object of the file

FileOutputStream output = new FileOutputStream(File fileObject);

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

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Methods of FileOutputStream

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

write() Method

• write() – writes the single byte to the file output stream
• write(byte[] array) – writes the bytes from the specified array to the output stream
• write(byte[] array, int start, int length) – writes the number of bytes equal to length to the output stream from an array starting from the position start
• Example: FileOutputStream to write data to a File

Example: FileOutputStream to write data to a File

import java.io.FileOutputStream;

public class Main {
    public static void main(String[] args) {
        
        String data = "This is a line of text inside the file.";

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

            byte[] array = data.getBytes();

            // Writes byte to the file
            output.write(array);

            output.close();
        }

        catch(Exception e) {
            e.getStackTrace();
        }
    }
}

In the above example, we have made a file output stream named output. The file output stream is connected with the file output.txt.

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

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

Here, when we run the program, the output.txt file is filled with the following content.

This is a line of text inside the file.

Note: The getBytes() method used in the program converts a string into an array of bytes.

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flush() Method

To clear the output stream, we can use the flush() strategy. This technique forces the output stream to write all data to the objective. For instance,

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 demo of flush method";

        try {
            out = new FileOutputStream(" flush.txt");

            // Using write() method
            out.write(data.getBytes());

            // Using the flush() method
            out.flush();
            out.close();
        }
        catch(Exception e) {
            e.getStackTrace();
        }
    }
}

When we run the program, the file flush.txt is filled with the text represented by the string data.

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close() Method

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

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Other Methods Of FileOutputStream

Methods	Descriptions
finalize()	ensures that the close() method is called
getChannel()	returns the object of FileChannel associated with the output stream
getFD()	returns the file descriptor associated with the output stream

To learn more, visit Java FileOutputStream (official Java documentation).

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Java I/O Streams