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

描述

如果输入数据缓冲区为空，java.util.zip.Deflater.needsInput() 方法返回 true，并且应该调用 setInput() 以提供更多输入。

声明

以下是 java.util.zip.Deflater.needsInput() 方法的声明。

public boolean needsInput()

返回值

如果输入数据缓冲区为空并且应该调用 setInput() 以提供更多输入，则为 true。

示例

以下示例展示了 java.util.zip.Deflater.needsInput() 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;";
      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());
   }
}

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 :42
Compressed Message Checksum :368538129
Compressed Message length : 42
UnCompressed Message Checksum :368538129
UnCompressed Message length : 300

❮ java.util.zip - Deflater 类