求一个数据库的压缩算法

[churencai]

有一个哈希表，里面存的是浮点类型的数据，现在需要一个压缩算法，对此哈希表进行压缩，在压缩状态下，能保证数据的正常读取。

[阁楼上的伟哥]

压缩以后还要解压 才行

[churencai]

就是在压缩状态下，不解压，因为要减小它的内存

[阁楼上的伟哥]

/***
  * 压缩GZip
  * 
  * @param data
  * @return
  */
 public static byte[] gZip(byte[] data) {
  byte[] b = null;
  try {
   ByteArrayOutputStream bos = new ByteArrayOutputStream();
   GZIPOutputStream gzip = new GZIPOutputStream(bos);
   gzip.write(data);
   gzip.finish();
   gzip.close();
   b = bos.toByteArray();
   bos.close();
  } catch (Exception ex) {
   ex.printStackTrace();
  }
  return b;
 }

 /***
  * 解压GZip
  * 
  * @param data
  * @return
  */
 public static byte[] unGZip(byte[] data) {
  byte[] b = null;
  try {
   ByteArrayInputStream bis = new ByteArrayInputStream(data);
   GZIPInputStream gzip = new GZIPInputStream(bis);
   byte[] buf = new byte[1024];
   int num = -1;
   ByteArrayOutputStream baos = new ByteArrayOutputStream();
   while ((num = gzip.read(buf, 0, buf.length)) != -1) {
    baos.write(buf, 0, num);
   }
   b = baos.toByteArray();
   baos.flush();
   baos.close();
   gzip.close();
   bis.close();
  } catch (Exception ex) {
   ex.printStackTrace();
  }
  return b;
 }

 /***
  * 压缩Zip
  * 
  * @param data
  * @return
  */
 public static byte[] zip(byte[] data) {
  byte[] b = null;
  try {
   ByteArrayOutputStream bos = new ByteArrayOutputStream();
   ZipOutputStream zip = new ZipOutputStream(bos);
   ZipEntry entry = new ZipEntry("zip");
   entry.setSize(data.length);
   zip.putNextEntry(entry);
   zip.write(data);
   zip.closeEntry();
   zip.close();
   b = bos.toByteArray();
   bos.close();
  } catch (Exception ex) {
   ex.printStackTrace();
  }
  return b;
 }

 /***
  * 解压Zip
  * 
  * @param data
  * @return
  */

 public static byte[] unZip(byte[] data) {
	  byte[] b = null;
	  try {
	   ByteArrayInputStream bis = new ByteArrayInputStream(data);
	   ZipInputStream zip = new ZipInputStream(bis);
	   while (zip.getNextEntry() != null) {
	    byte[] buf = new byte[1024];
	    int num = -1;
	    ByteArrayOutputStream baos = new ByteArrayOutputStream();
	    while ((num = zip.read(buf, 0, buf.length)) != -1) {
	     baos.write(buf, 0, num);
	    }
	    b = baos.toByteArray();
	    baos.flush();
	    baos.close();
	   }
	   zip.close();
	   bis.close();
	  } catch (Exception ex) {
	   ex.printStackTrace();
	  }
	  return b;
	 }

 /***
  * 压缩BZip2
  * 
  * @param data
  * @return
  */
 public static byte[] bZip2(byte[] data) {
  byte[] b = null;
  try {
   ByteArrayOutputStream bos = new ByteArrayOutputStream();
   CBZip2OutputStream bzip2 = new CBZip2OutputStream(bos);
   bzip2.write(data);
   bzip2.flush();
   bzip2.close();
   b = bos.toByteArray();
   bos.close();
  } catch (Exception ex) {
   ex.printStackTrace();
  }
  return b;
 }

 /***
  * 解压BZip2
  * 
  * @param data
  * @return
  */
 public static byte[] unBZip2(byte[] data) {
  byte[] b = null;
  try {
   ByteArrayInputStream bis = new ByteArrayInputStream(data);
   CBZip2InputStream bzip2 = new CBZip2InputStream(bis);
   byte[] buf = new byte[1024];
   int num = -1;
   ByteArrayOutputStream baos = new ByteArrayOutputStream();
   while ((num = bzip2.read(buf, 0, buf.length)) != -1) {
    baos.write(buf, 0, num);
   }
   b = baos.toByteArray();
   baos.flush();
   baos.close();
   bzip2.close();
   bis.close();
  } catch (Exception ex) {
   ex.printStackTrace();
  }
  return b;
 }

参数都是字节的形式。上面的方法你参考一下吧。是zip压缩的。
你说那个 没研究过……