java.util.zip.Deflater setDictionary()方法

java.util.zip.Deflater setDictionary()方法 介绍

java.util.zip.Deflater.setDictionary() 方法设置预置字典压缩。当可以预先确定历史缓冲区时，使用预设字典。当稍后使用 Inflater.inflate() 解压缩数据时，可以调用 Inflater.getAdler() 以获取解压缩所需的字典的 Adler-32 值。

java.util.zip.Deflater setDictionary()方法 声明

public void setDictionary(byte[] b)

java.util.zip.Deflater setDictionary()方法 参数

• b ： 字典数据字节。

java.util.zip.Deflater setDictionary()方法 返回值

写入输出缓冲区的压缩数据的实际字节数。

java.util.zip.Deflater setDictionary()方法 示例

下面的例子展示了 java.util.zip.Deflater.setDictionary()方法的用法。

package com.yiidian;

import java.io.UnsupportedEncodingException;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.Inflater;

public class DeflaterDemo {
   public static void main(String[] args) 
      throws DataFormatException, UnsupportedEncodingException {
      String message = "Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;"
         +"Welcome to Yiidian.com;";
      String dictionary = "Welcome";
 
      System.out.println("Original Message length : " + message.length());
      byte[] input = message.getBytes("UTF-8");

      // Compress the bytes
      byte[] output = new byte[1024];
      Deflater deflater = new Deflater();
      deflater.setDictionary(dictionary.getBytes("UTF-8"));
      deflater.setInput(input);
   
      deflater.finish();
      int compressedDataLength = deflater.deflate(output,0 , output.length, Deflater.NO_FLUSH);
      System.out.println("Total uncompressed bytes output :" + deflater.getTotalOut());
      System.out.println("Compressed Message Checksum :" + deflater.getAdler());     
      deflater.finished();

      System.out.println("Compressed Message length : " + compressedDataLength);

      // Decompress the bytes
      Inflater inflater = new Inflater();
      inflater.setInput(output, 0, compressedDataLength);
      byte[] result = new byte[1024];
      int resultLength = inflater.inflate(result);
      if(inflater.needsDictionary()){
    
         inflater.setDictionary(dictionary.getBytes("UTF-8"));
 
         resultLength = inflater.inflate(result);
      }
      inflater.finished();

      // Decode the bytes into a String
      message = new String(result, 0, resultLength, "UTF-8");
      System.out.println("UnCompressed Message Checksum :" + inflater.getAdler());  
      System.out.println("UnCompressed Message length : " + message.length());
   }
}

输出结果为：