java解压zip文件示例

若是使用Java自带的压缩工具包来实现解压缩文件到指定文件夹的功能，因为jdk提供的zip只能按UTF-8格式处理，而Windows系统中文件名是以GBK方式编码的，所以如果是解压一个包含中文文件名的zip包，会报非法参数异常，所以要实现解压缩，就得对DeflaterOutputStream.java、InflaterInputStream.java、ZipConstants.java、ZipEntry.java、ZipInputStream.java以及ZipOutputStream.java这些相关的类进行修改，过程如下：
因为从 J2SE 1.4 开始，Java 编译器不再支持 import 进未命包名的类、接口，所以在创建的Java项目中，一定要新建一个自己定义的包，包命名的格式一般为学校域名的逆序+自己的网名，比如cn.edu.xidian.crytoll。
在包内新建DeflaterOutputStream类，代码如下：

DeflaterOutputStream.java:

复制代码 代码如下:
package cn.edu.xdian.crytoll;

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


public
class DeflaterOutputStream extends FilterOutputStream {
    
    protected Deflater def;

    
    protected byte[] buf;

    

    private boolean closed = false;

    
    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];
    }

    
    public DeflaterOutputStream(OutputStream out, Deflater def) {
    this(out, def, 512);
    }

    boolean usesDefaultDeflater = false;

    
    public DeflaterOutputStream(OutputStream out) {
    this(out, new Deflater());
        usesDefaultDeflater = true;
    }

    
    public void write(int b) throws IOException {
        byte[] buf = new byte[1];
    buf[0] = (byte)(b & 0xff);
    write(buf, 0, 1);
    }

    
    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();
                }
            }
    }
    }

    
    public void finish() throws IOException {
    if (!def.finished()) {
        def.finish();
        while (!def.finished()) {
        deflate();
        }
    }
    }

    
    public void close() throws IOException {
        if (!closed) {
            finish();
            if (usesDefaultDeflater)
                def.end();
            out.close();
            closed = true;
        }
    }

    
    protected void deflate() throws IOException {
    int len = def.deflate(buf, 0, buf.length);
    if (len > 0) {
        out.write(buf, 0, len);
    }
    }
}