Question

I am trying to use the following Java code to compress and uncompress a String. But the line that creates a new GZipInputStream object out of a new ByteArrayInputStream object throws a “java.util.zip.ZipException: Not in GZIP format” exception. Does anyone know how to solve this?

        String orig = ".............";

        // compress it
        ByteArrayOutputStream baostream = new ByteArrayOutputStream();
        OutputStream outStream = new GZIPOutputStream(baostream);
        outStream.write(orig.getBytes());
        outStream.close();
        String compressedStr = baostream.toString();

        // uncompress it
        InputStream inStream = new GZIPInputStream(new ByteArrayInputStream(compressedStr.getBytes()));
        ByteArrayOutputStream baoStream2 = new ByteArrayOutputStream();
        byte[] buffer = new byte[8192];
        int len;
        while((len = inStream.read(buffer))>0)
            baoStream2.write(buffer, 0, len);
        String uncompressedStr = baoStream2.toString();

Answer 1

Mixing String and byte[]; that does never fit. And only works on the the same OS with same encoding. Not every byte[] can be converted to a String, and the conversion back could give other bytes.

The compressedBytes need not represent a String.

Explicitly set the encoding in getBytes and new String.

    String orig = ".............";

    // Compress it
    ByteArrayOutputStream baostream = new ByteArrayOutputStream();
    OutputStream outStream = new GZIPOutputStream(baostream);
    outStream.write(orig.getBytes("UTF-8"));
    outStream.close();
    byte[] compressedBytes = baostream.toByteArray(); // toString not always possible

    // Uncompress it
    InputStream inStream = new GZIPInputStream(
            new ByteArrayInputStream(compressedBytes));
    ByteArrayOutputStream baoStream2 = new ByteArrayOutputStream();
    byte[] buffer = new byte[8192];
    int len;
    while ((len = inStream.read(buffer)) > 0) {
        baoStream2.write(buffer, 0, len);
    }
    String uncompressedStr = baoStream2.toString("UTF-8");

    System.out.println("orig: " + orig);
    System.out.println("unc:  " + uncompressedStr);