java.util.zip.Deflater.needsInput()方法範例

java.util.zip.Deflater.needsInput()方法如果輸入資料緩衝區為空則返回true，並且應該呼叫setInput()以提供更多輸入。

宣告

以下是java.util.zip.Deflater.needsInput()方法的宣告。

public boolean needsInput()

引數

• N/A

返回值

• 如果輸入資料緩衝區為空則返回true，並且應該呼叫setInput()以提供更多輸入。

範例

以下範例顯示了java.util.zip.Deflater.needsInput()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;";
      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();
      int inCount = input.length;  
      int inPosition = 0;
      int outPosition = 0;

      int MAX_BUFFER_SIZE = 10;
      while(!deflater.finished()){
         int want = -1;
         int got;
         if (deflater.needsInput() && inCount != 0) {
            want = (inCount < MAX_BUFFER_SIZE) ? inCount : MAX_BUFFER_SIZE;

            deflater.setInput(input, inPosition, want);

            inCount -= want;
            inPosition += want;
            if (inCount == 0) {
               deflater.finish();
            }
         }
         // deflate to current position in output buffer
         int compCount;

         compCount = deflater.deflate(output, outPosition, MAX_BUFFER_SIZE);
         outPosition += compCount;
      }

      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 : " + outPosition);

      // Decompress the bytes
      Inflater inflater = new Inflater();
      inflater.setInput(output, 0, outPosition);
      byte[] result = new byte[1024];
      int 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