通道Channel獲取四種方法

package com.hp.buffer;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

import org.junit.Test;

public class TextChannel {

	@Test //獲得通道方法一：用getChannel()方法（非直接緩沖區）
	public void text1() throws IOException {
			
		FileInputStream fis = null;
		FileOutputStream fos = null;
		FileChannel inChannel = null;
		FileChannel outChannel = null;
		long start = System.currentTimeMillis();
		try {	
			//輸入輸出流
			fis = new FileInputStream("D:\\6.jpg");
			fos = new FileOutputStream("D:\\8.jpg");
			//通道
			inChannel = fis.getChannel();
			outChannel = fos.getChannel();
			//緩沖區
			ByteBuffer buffer = ByteBuffer.allocate(1024);
			
			//把通道里面的數據，讀出來，放緩沖區里面
			while(inChannel.read(buffer)!= -1) {
				//把緩沖區里面的數據，寫入，到通道里面
				buffer.flip();
				outChannel.write(buffer);
				buffer.clear();//清空緩存區
			}
		
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			//對通道和流進行關閉
			  if(outChannel!=null) {
				  outChannel.close();
			  }
			  if(inChannel!=null) {
				  outChannel.close();
			  }
			  if(fos!=null) {
				  fos.close();
			  }
			  if(fis!=null) {
				  fis.close();
			  }	 
		}
		long end = System.currentTimeMillis();
		System.out.println(end-start);
	}	
	
	//獲得通道方法二：靜態open()方法，獲取FileChannel對象，
	//(直接緩沖區:不用寫在應用程序的內存里面，直接寫在物理地址上面)
	@Test
	public void test2() throws Exception {
		
		
		FileChannel	 inChannel = FileChannel.open(Paths.get("D:\\6.jpg"), StandardOpenOption.READ);
		
		MappedByteBuffer inmap = inChannel.map(MapMode.READ_ONLY, 0, inChannel.size());
		
		FileChannel	 outChannel = FileChannel.open(Paths.get("D:\\9.jpg"), StandardOpenOption.READ,StandardOpenOption.WRITE,StandardOpenOption.CREATE_NEW);
		
		MappedByteBuffer outmap = outChannel.map(MapMode.READ_WRITE , 0, inChannel.size());
		
		long start = System.currentTimeMillis();
		//對緩沖區域的數據進行操作
		byte[] dst = new byte[inmap.limit()];
		inmap.get(dst);
		outmap.put(dst);
		
		outChannel.close();
		inChannel.close();
		
		long end = System.currentTimeMillis();
		System.out.println(end-start);
	}
	
	//transferTo() /transferForm()  (直接緩沖區)
	@Test
	public void test3() throws Exception {
		
		FileChannel inFile = FileChannel.open(Paths.get("D:\\6.jpg"), StandardOpenOption.READ);
		
		FileChannel outFile = FileChannel.open(Paths.get("D:\\10.jpg"), StandardOpenOption.READ,StandardOpenOption.WRITE,StandardOpenOption.CREATE);
		
		inFile.transferTo(0, inFile.size(), outFile);
		
		outFile.close();
		inFile.close();
	}
	
	
	  @Test //從流中獲取通道,采用allocateDirect方式（直接緩沖區）
	public void test4() throws Exception {
	  
	  FileChannel inFile = FileChannel.open(Paths.get("D:\\6.jpg"),
	  StandardOpenOption.READ);
	  
	  FileChannel outFile = FileChannel.open(Paths.get("D:\\11.jpg"),
	  StandardOpenOption.READ,StandardOpenOption.WRITE,StandardOpenOption.CREATE);
	  
	  ByteBuffer buffer = ByteBuffer.allocateDirect((int)inFile.size());
	  
	  inFile.read(buffer);	  
	  buffer.flip();  //切換
	  outFile.write(buffer);
	  
	  outFile.close();
	  inFile.close();
	}
	 
	
	
}