In this quick article, you'll learn how to convert an instance of InputStream to a file using Java. In Java, there are several ways to do this conversion as explained below.

Using Files.copy() Method

In Java 7 or higher, you can use the Files.copy() method from Java's NIO API to copy an InputStream object to a file as shown below:

try (InputStream stream = Files.newInputStream(Paths.get("input.txt"))) {

    // convert stream to file
    Files.copy(stream, Paths.get("output.txt"));

} catch (IOException ex) {
    ex.printStackTrace();
}

The above code will throw an error if the file already exists. To replace the existing file, you can use the below example code:

try (InputStream stream = Files.newInputStream(Paths.get("input.txt"))) {

    // convert stream to file
    Files.copy(stream, Paths.get("output.txt"), StandardCopyOption.REPLACE_EXISTING);

} catch (IOException ex) {
    ex.printStackTrace();
}

Using OutputStream Class

In Java 6 or below, you can use the OutputStream class to manually copy data from InputStream to a file as shown below:

try (InputStream inputStream = new FileInputStream(new File("input.txt"));
     OutputStream outputStream = new FileOutputStream(new File("output.txt"))) {
        int length;
        byte[] bytes = new byte[1024];
        // copy data from input stream to output stream
        while ((length = inputStream.read(bytes)) != -1) {
            outputStream.write(bytes, 0, length);
        }

} catch (IOException ex) {
    ex.printStackTrace();
}

Using Apache Commons IO

The Apache Commons IO library provides IOUtils.copyInputStreamToFile() method to easily copy an instance of InputStream to a file as shown below:

try (InputStream stream = Files.newInputStream(Paths.get("input.txt"))) {

    // convert input stream to file
    FileUtils.copyInputStreamToFile(stream, new File("output.txt"));

} catch (IOException ex) {
    ex.printStackTrace();
}

Don't forget to include Apache Commons IO dependency to your Maven's project pom.xml file:

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.6</version>
</dependency>

For a Gradle project, add the following dependency to your build.gralde file:

implementation 'commons-io:commons-io:2.6'

Further Reading

You may be interested in other Java I/O articles:

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