(Java) 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.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    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) {
        System.out.println(gzip.lastErrorText());
        return;
        }

    System.out.println("Compression successful.");
    System.out.println("Gzip file created: " + outputFile);
  }
}