java.util.zip.Deflater.setDictionary() 方法
描述
java.util.zip.Deflater.setDictionary(byte[] b, int off, int len) 方法设置用于压缩的预设字典。 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。
声明
以下是 java.util.zip.Deflater.setDictionary(byte[] b, int off, int len) 方法的声明。
public void setDictionary(byte[] b, int off, int len)
参数
b − 字典数据字节。
off − 数据的起始偏移量。
len − 数据的长度。
示例
以下示例显示了 java.util.zip.Deflater.setDictionary(byte[] b, int off, int len) 方法的用法。
package com.tutorialspoint;
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 TutorialsPoint.com;"
+"Welcome to TutorialsPoint.com;"
+"Welcome to TutorialsPoint.com;"
+"Welcome to TutorialsPoint.com;"
+"Welcome to TutorialsPoint.com;"
+"Welcome to TutorialsPoint.com;"
+"Welcome to TutorialsPoint.com;"
+"Welcome to TutorialsPoint.com;"
+"Welcome to TutorialsPoint.com;"
+"Welcome to TutorialsPoint.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"),0, dictionary.length());
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"),0, dictionary.length());
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());
}
}
让我们编译并运行上面的程序，这将产生下面的结果 −
Original Message length : 300 Total uncompressed bytes output :40 Compressed Message Checksum :368538129 Compressed Message length : 40 UnCompressed Message Checksum :368538129 UnCompressed Message length : 300
