(Android™) Compress a File to Gzip with Custom Metadata

See more Gzip Examples

This example demonstrates how to use the CompressFile method to create a Gzip (.gz) file while customizing the metadata embedded in the Gzip header.

Before compression, several properties are set:

• Comment: Adds a descriptive comment to the Gzip file.
• Filename: Specifies the filename to embed in the Gzip data, which may be used by extraction tools as the default output name.
• CompressionLevel: Controls the tradeoff between compression ratio and speed (set to maximum in this example).
• LastModStr: Sets the last-modified timestamp using an RFC 822 formatted date string.

After setting these properties, the input file is compressed and written to a .gz file. This approach allows you to embed meaningful metadata along with the compressed data.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    boolean success = false;

    // This example demonstrates how to compress a file to Gzip format
    // while setting custom metadata such as comment, filename,
    // compression level, and last-modified date.

    CkGzip gzip = new CkGzip();

    // Set custom Gzip properties:
    gzip.put_Comment("Example Gzip file created with Chilkat");
    gzip.put_Filename("custom_name.txt");
    gzip.put_CompressionLevel(9);
    gzip.put_LastModStr("Wed, 1 Apr 2025 12:45:26 -0500");

    // The file to be compressed:
    String inputFile = "example.txt";
    String outputFile = "example.txt.gz";

    // Compress the file:
    success = gzip.CompressFile(inputFile,outputFile);
    if (success == false) {
        Log.i(TAG, gzip.lastErrorText());
        return;
        }

    Log.i(TAG, "Compression successful.");
    Log.i(TAG, "Gzip file created: " + outputFile);

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}