Java压缩/解压缩二进制文件

在Java中提供Deflater和Inflater工具类来压缩/解压缩数据。 这两个工具类采用zlib算法，下面给出一个封装好的工具。

/** * util for compress/decompress data *  * @author lichengwu * @version 1.0 * @created 2013-02-07 10:14 AM */public final class CompressionUtil {    private static final int BUFFER_SIZE = 4 * 1024;    /**     * compress data by {@linkplain Level}     *      * @author lichengwu     * @created 2013-02-07     *      * @param data     * @param level     *            see {@link Level}     * @return     * @throws IOException     */    public static byte[] compress(byte[] data, Level level) throws IOException {        Assert.notNull(data);        Assert.notNull(level);        Deflater deflater = new Deflater();        // set compression level        deflater.setLevel(level.getLevel());        deflater.setInput(data);        ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);        deflater.finish();        byte[] buffer = new byte[BUFFER_SIZE];        while (!deflater.finished()) {            int count = deflater.deflate(buffer); // returns the generated                                                  // code... index            outputStream.write(buffer, 0, count);        }        byte[] output = outputStream.toByteArray();outputStream.close();        return output;    }    /**     * decompress data     *      * @author lichengwu     * @created 2013-02-07     *      * @param data     * @return     * @throws IOException     * @throws DataFormatException     */    public static byte[] decompress(byte[] data) throws IOException, DataFormatException {        Assert.notNull(data);        Inflater inflater = new Inflater();        inflater.setInput(data);        ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);        byte[] buffer = new byte[BUFFER_SIZE];        while (!inflater.finished()) {            int count = inflater.inflate(buffer);            outputStream.write(buffer, 0, count);        }        byte[] output = outputStream.toByteArray();outputStream.close();        return output;    }    /**     * Compression level     */    public static enum Level {        /**         * Compression level for no compression.         */        NO_COMPRESSION(0),        /**         * Compression level for fastest compression.         */        BEST_SPEED(1),        /**         * Compression level for best compression.         */        BEST_COMPRESSION(9),        /**         * Default compression level.         */        DEFAULT_COMPRESSION(-1);        private int level;        Level(        int level) {            this.level = level;        }        public int getLevel() {            return level;        }    }  }

下面是一个测试：

@Testpublic void testCompress() throws Exception {    BufferedInputStream in = new BufferedInputStream(new FileInputStream(            "/Users/lichengwu/tmp/out_put.txt.bak"));    ByteArrayOutputStream out = new ByteArrayOutputStream(1024);    byte[] temp = new byte[1024];    int size = 0;    while ((size = in.read(temp)) != -1) {        out.write(temp, 0, size);    }    in.close();    byte[] data = out.toByteArray();    byte[] output = CompressionUtil.compress(data, CompressionUtil.Level.BEST_COMPRESSION);    System.out.println("before : " + (data.length / 1024) + "k");    System.out.println("after : " + (output.length / 1024) + "k");    FileOutputStream fos = new FileOutputStream("/Users/lichengwu/tmp/out_put.txt.bak.compress");    fos.write(output);    out.close();    fos.close();}@Testpublic void testDecompress() throws Exception {    BufferedInputStream in = new BufferedInputStream(new FileInputStream(            "/Users/lichengwu/tmp/out_put.txt.bak.compress"));    ByteArrayOutputStream out = new ByteArrayOutputStream(1024);    byte[] temp = new byte[1024];    int size = 0;    while ((size = in.read(temp)) != -1) {        out.write(temp, 0, size);    }    in.close();    byte[] data = out.toByteArray();    byte[] output = CompressionUtil.decompress(data);    System.out.println("before : " + (data.length / 1024) + "k");    System.out.println("after : " + (output.length / 1024) + "k");    FileOutputStream fos = new FileOutputStream("/Users/lichengwu/tmp/out_put.txt.bak.decompress");    fos.write(output);    out.close();    fos.close();}

关于OutOfMemoryError，请参考：http://www.devguli.com/blog/eng/java-deflater-and-outofmemoryerror/