Delete contents of a file without deleting itself in Java

This post will discuss how to delete the contents of a file without deleting the file itself in Java.

1. Using `BufferedWriter`

A simple solution is to get a BufferedWriter with the Files.newBufferedWriter(…) method with the TRUNCATE_EXISTING standard open option. It truncates the file to length 0 if it already exists (when opened for writing).

The complete usage is demonstrated below using try-with-resource statement (Java 7+), which automatically take care of closing the opened streams and channels:

import java.io.BufferedWriter;

import java.io.IOException;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.StandardOpenOption;

public class Main {

public static void main(String[] args) {

String fileName = "/user/data/sys.log";

try (BufferedWriter bf = Files.newBufferedWriter(Path.of(fileName),

StandardOpenOption.TRUNCATE_EXISTING)) {

} catch (IOException e) {

e.printStackTrace();

}

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2. Using `PrintWriter`

Alternatively, you can create a new PrintWriter with the specified file name. It results in a file truncated to size zero if it already exists.

import java.io.IOException;

import java.io.PrintWriter;

public class Main {

public static void main(String[] args) {

String fileName = "/user/data/sys.log";

try {

PrintWriter pw = new PrintWriter(fileName);

pw.close();

} catch (IOException e) {

e.printStackTrace();

}

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Here’s an equivalent version with try-with-resource statement, which take care of closing the stream:

import java.io.IOException;

import java.io.PrintWriter;

public class Main {

public static void main(String[] args) {

String fileName = "/user/data/sys.log";

try (PrintWriter pw = new PrintWriter(fileName)){

} catch (IOException e) {

e.printStackTrace();

}

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3. Using `FileChannel`

The FileChannel class provides the truncate() method that can truncate a file to the given size. Its usage is demonstrated below:

import java.io.IOException;

import java.nio.channels.FileChannel;

import java.nio.file.Path;

import java.nio.file.StandardOpenOption;

public class Main {

public static void main(String[] args) {

String fileName = "/user/data/sys.log";

try {

FileChannel.open(Path.of(fileName), StandardOpenOption.WRITE)

.truncate(0).close();

} catch (IOException e) {

e.printStackTrace();

}

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4. Using `RandomAccessFile`

With the RandomAccessFile class, you can set the length of a file using the setLength() method. To truncate the file, pass the length of the file as 0, as shown below:

import java.io.IOException;

import java.io.RandomAccessFile;

public class Main {

public static void main(String[] args) {

String fileName = "/user/data/sys.log";

try (RandomAccessFile raf = new RandomAccessFile(fileName, "rw")) {

raf.setLength(0);

}

catch (IOException e) {

e.printStackTrace();

}

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5. Using `FileOutputStream`

Finally, you can use FileOutputStream to truncate a file to length 0 if it exists. A typical invocation for this class would look like:

import java.io.FileOutputStream;

import java.io.IOException;

public class Main {

public static void main(String[] args) {

String fileName = "/user/data/sys.log";

try (FileOutputStream fos = new FileOutputStream(fileName, false)) { }

catch (IOException e) {

e.printStackTrace();

}

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That’s all about deleting the contents of a file without deleting the file itself in Java.

Delete contents of a file without deleting itself in Java

1. Using BufferedWriter

2. Using PrintWriter

3. Using FileChannel

4. Using RandomAccessFile

5. Using FileOutputStream

Share this:

1. Using `BufferedWriter`

2. Using `PrintWriter`

3. Using `FileChannel`

4. Using `RandomAccessFile`

5. Using `FileOutputStream`