java.util.zip.Deflater.setDictionary(byte[] b, int off, int len)
方法設定預設字典進行壓縮。 當可以預先確定歷史緩衝器時使用預設字典。 當資料隨後使用Inflater.inflate()
進行解壓縮時,可以呼叫Inflater.getAdler()
以獲取解壓縮所需的字典的Adler-32值。
宣告
以下是java.util.zip.Deflater.setDictionary(byte[] b, int off, int len)
方法的宣告。
public void setDictionary(byte[] b, int off, int len)
引數
b
- 字典資料位元組。off
- 資料的起始偏移量。len
- 資料的長度。返回值
範例
以下範例顯示了java.util.zip.Deflater.setDictionary(byte[] b, int off, int len)
方法的用法。
package com.yiibai;
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 Tw511.com;"
+"Welcome to Tw511.com;"
+"Welcome to Tw511.com;"
+"Welcome to Tw511.com;"
+"Welcome to Tw511.com;"
+"Welcome to Tw511.com;"
+"Welcome to Tw511.com;"
+"Welcome to Tw511.com;"
+"Welcome to Tw511.com;"
+"Welcome to Tw511.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());
}
}
執行上面範例程式碼,得到以下結果 -
Original Message length : 300
Total uncompressed bytes output :42
Compressed Message Checksum :368538129
Compressed Message length : 42
UnCompressed Message Checksum :368538129
UnCompressed Message length : 300