GZIP

第一种：返回字节数组

	// 压缩
	  public static byte[] compress(String str) throws IOException {
		  Log.i(TAG,"--- compress() start ---");
		  
		  if (str == null || str.length() == 0) {
		      return null;
		  }
		  ByteArrayOutputStream out = new ByteArrayOutputStream();
		  GZIPOutputStream gzip = new GZIPOutputStream(out);
		  gzip.write(str.getBytes("UTF-8"));
		  gzip.close();
		 
		  Log.i(TAG,"--- compress() end ---");
		  return out.toByteArray();
	  }

     // 解压缩
     public static String decompress(InputStream is) throws IOException {
		  Log.i(TAG,"--- decompress() start ---");
		  
		  ByteArrayOutputStream out = new ByteArrayOutputStream();
		  GZIPInputStream gunzip = new GZIPInputStream(is);
		  byte[] buffer = new byte[BUFFER_SIZE];
		  int n;
		  while ((n = gunzip.read(buffer)) >= 0) {
			  out.write(buffer, 0, n);
		  }
    
		  Log.i(TAG,"--- decompress() end ---");
		  return out.toString("UTF-8");
	  }

          //解压缩的出来的文件如果是文本文件的话，还可以一行一行的处理
 public static void decompress(InputStream is)
	throws Exception {
		GZIPInputStream gis = new GZIPInputStream(is);
		BufferedReader reader = new BufferedReader(new InputStreamReader(gis,"GBK"));
		try {
            String line;
            while((line = reader.readLine()) != null) {
            	//处理每行数据
            }
        } finally {
            reader.close();
            gis.close();
        }
	}

第二种：返回字符串
1、使用ISO-8859-1作为中介编码，可以保证准确还原数据
2、字符编码确定时，可以在uncompress方法最后一句中显式指定编码

	public static String compress(String str) {
		byte[] output = new byte[10000];
		Deflater compresser = new Deflater();
		compresser.setInput(str.getBytes());
		compresser.finish();
		
		int compressDataLength = compresser.deflate(output);
		String s = null;
		try {
			s = new String(output, 0, compressDataLength, "UTF-8");
		} catch (UnsupportedEncodingException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return s;
	}	  

        public static String decompress(String str) throws IOException {
	    if (str == null || str.length() == 0) {
	      return str;
	    }
	    ByteArrayOutputStream out = new ByteArrayOutputStream();
	    ByteArrayInputStream in = new ByteArrayInputStream(str
	        .getBytes("ISO-8859-1"));
	    GZIPInputStream gunzip = new GZIPInputStream(in);
	    byte[] buffer = new byte[1024];
	    int n;
	    while ((n = gunzip.read(buffer)) >= 0) {
	      out.write(buffer, 0, n);
	    }
	    // toString()使用平台默认编码，也可以显式的指定如toString("GBK")
	    return out.toString();
	  }

三、如下是从一个网站上偷来的

package org.zlex.commons.io;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;
/**
 * GZIP工具
 * 
 * @author <a href="mailto:[e-mail]">梁栋</a>
 * @since 1.0
 */
public abstract class GZipUtils {
	public static final int BUFFER = 1024;
	public static final String EXT = ".gz";
	/**
	 * 数据压缩
	 * 
	 * @param data
	 * @return
	 * @throws Exception
	 */
	public static byte[] compress(byte[] data) throws Exception {
		ByteArrayInputStream bais = new ByteArrayInputStream(data);
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		// 压缩
		compress(bais, baos);
		byte[] output = baos.toByteArray();
		baos.flush();
		baos.close();
		bais.close();
		return output;
	}
	/**
	 * 文件压缩
	 * 
	 * @param file
	 * @throws Exception
	 */
	public static void compress(File file) throws Exception {
		compress(file, true);
	}
	/**
	 * 文件压缩
	 * 
	 * @param file
	 * @param delete
	 *            是否删除原始文件
	 * @throws Exception
	 */
	public static void compress(File file, boolean delete) throws Exception {
		FileInputStream fis = new FileInputStream(file);
		FileOutputStream fos = new FileOutputStream(file.getPath() + EXT);
		compress(fis, fos);
		fis.close();
		fos.flush();
		fos.close();
		if (delete) {
			file.delete();
		}
	}
	/**
	 * 数据压缩
	 * 
	 * @param is
	 * @param os
	 * @throws Exception
	 */
	public static void compress(InputStream is, OutputStream os)
			throws Exception {
		GZIPOutputStream gos = new GZIPOutputStream(os);
		int count;
		byte data[] = new byte[BUFFER];
		while ((count = is.read(data, 0, BUFFER)) != -1) {
			gos.write(data, 0, count);
		}
		gos.finish();
		gos.flush();
		gos.close();
	}
	/**
	 * 文件压缩
	 * 
	 * @param path
	 * @throws Exception
	 */
	public static void compress(String path) throws Exception {
		compress(path, true);
	}
	/**
	 * 文件压缩
	 * 
	 * @param path
	 * @param delete
	 *            是否删除原始文件
	 * @throws Exception
	 */
	public static void compress(String path, boolean delete) throws Exception {
		File file = new File(path);
		compress(file, delete);
	}
	/**
	 * 数据解压缩
	 * 
	 * @param data
	 * @return
	 * @throws Exception
	 */
	public static byte[] decompress(byte[] data) throws Exception {
		ByteArrayInputStream bais = new ByteArrayInputStream(data);
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		// 解压缩
		decompress(bais, baos);
		data = baos.toByteArray();
		baos.flush();
		baos.close();
		bais.close();
		return data;
	}
	/**
	 * 文件解压缩
	 * 
	 * @param file
	 * @throws Exception
	 */
	public static void decompress(File file) throws Exception {
		decompress(file, true);
	}
	/**
	 * 文件解压缩
	 * 
	 * @param file
	 * @param delete
	 *            是否删除原始文件
	 * @throws Exception
	 */
	public static void decompress(File file, boolean delete) throws Exception {
		FileInputStream fis = new FileInputStream(file);
		FileOutputStream fos = new FileOutputStream(file.getPath().replace(EXT,
				""));
		decompress(fis, fos);
		fis.close();
		fos.flush();
		fos.close();
		if (delete) {
			file.delete();
		}
	}
	/**
	 * 数据解压缩
	 * 
	 * @param is
	 * @param os
	 * @throws Exception
	 */
	public static void decompress(InputStream is, OutputStream os)
			throws Exception {
		GZIPInputStream gis = new GZIPInputStream(is);
		int count;
		byte data[] = new byte[BUFFER];
		while ((count = gis.read(data, 0, BUFFER)) != -1) {
			os.write(data, 0, count);
		}
		gis.close();
	}
	/**
	 * 文件解压缩
	 * 
	 * @param path
	 * @throws Exception
	 */
	public static void decompress(String path) throws Exception {
		decompress(path, true);
	}
	/**
	 * 文件解压缩
	 * 
	 * @param path
	 * @param delete
	 *            是否删除原始文件
	 * @throws Exception
	 */
	public static void decompress(String path, boolean delete) throws Exception {
		File file = new File(path);
		decompress(file, delete);
	}
}