java解压zip文件示例

package cn.edu.xdian.crytoll;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.Deflater;

/**
 * This class implements an output stream filter for compressing data in
 * the "deflate" compression format. It is also used as the basis for other
 * types of compression filters, such as GZIPOutputStream.
 *
 * @see     Deflater
 * @version     1.36, 03/13/06
 * @author  David Connelly
 */
public
class DeflaterOutputStream extends FilterOutputStream {
    /**
     * Compressor for this stream.
     */
    protected Deflater def;

    /**
     * Output buffer for writing compressed data.
     */
    protected byte[] buf;

    /**
     * Indicates that the stream has been closed.
     */

    private boolean closed = false;

    /**
     * Creates a new output stream with the specified compressor and
     * buffer size.
     * @param out the output stream
     * @param def the compressor ("deflater")
     * @param size the output buffer size
     * @exception IllegalArgumentException if size is <= 0
     */
    public DeflaterOutputStream(OutputStream out, Deflater def, int size) {
        super(out);
        if (out == null || def == null) {
            throw new NullPointerException();
        } else if (size <= 0) {
            throw new IllegalArgumentException("buffer size <= 0");
        }
        this.def = def;
        buf = new byte[size];
    }

    /**
     * Creates a new output stream with the specified compressor and
     * a default buffer size.
     * @param out the output stream
     * @param def the compressor ("deflater")
     */
    public DeflaterOutputStream(OutputStream out, Deflater def) {
    this(out, def, 512);
    }

    boolean usesDefaultDeflater = false;

    /**
     * Creates a new output stream with a default compressor and buffer size.
     * @param out the output stream
     */
    public DeflaterOutputStream(OutputStream out) {
    this(out, new Deflater());
        usesDefaultDeflater = true;
    }

    /**
     * Writes a byte to the compressed output stream. This method will
     * block until the byte can be written.
     * @param b the byte to be written
     * @exception IOException if an I/O error has occurred
     */
    public void write(int b) throws IOException {
        byte[] buf = new byte[1];
    buf[0] = (byte)(b & 0xff);
    write(buf, 0, 1);
    }

    /**
     * Writes an array of bytes to the compressed output stream. This
     * method will block until all the bytes are written.
     * @param b the data to be written
     * @param off the start offset of the data
     * @param len the length of the data
     * @exception IOException if an I/O error has occurred
     */
    public void write(byte[] b, int off, int len) throws IOException {
    if (def.finished()) {
        throw new IOException("write beyond end of stream");
    }
        if ((off | len | (off + len) | (b.length - (off + len))) < 0) {
        throw new IndexOutOfBoundsException();
    } else if (len == 0) {
        return;
    }
    if (!def.finished()) {
            // Deflate no more than stride bytes at a time.  This avoids
            // excess copying in deflateBytes (see Deflater.c)
            int stride = buf.length;
            for (int i = 0; i < len; i+= stride) {
                def.setInput(b, off + i, Math.min(stride, len - i));
                while (!def.needsInput()) {
                    deflate();
                }
            }
    }
    }

    /**
     * Finishes writing compressed data to the output stream without closing
     * the underlying stream. Use this method when applying multiple filters
     * in succession to the same output stream.
     * @exception IOException if an I/O error has occurred
     */
    public void finish() throws IOException {
    if (!def.finished()) {
        def.finish();
        while (!def.finished()) {
        deflate();
        }
    }
    }

    /**
     * Writes remaining compressed data to the output stream and closes the
     * underlying stream.
     * @exception IOException if an I/O error has occurred
     */
    public void close() throws IOException {
        if (!closed) {
            finish();
            if (usesDefaultDeflater)
                def.end();
            out.close();
            closed = true;
        }
    }

    /**
     * Writes next block of compressed data to the output stream.
     * @throws IOException if an I/O error has occurred
     */
    protected void deflate() throws IOException {
    int len = def.deflate(buf, 0, buf.length);
    if (len > 0) {
        out.write(buf, 0, len);
    }
    }
}