package newio;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

/*
 * 分别采用新旧I/O包的API复制文件,比较性能
 */
public class CopyFileCompara {

	public void copyFileOld(File from,File to) throws IOException{
		//使用传统的I/O流处理(加了缓冲机制)
		FileInputStream fin=new FileInputStream(from);
		FileOutputStream fout=new FileOutputStream(to);
		BufferedInputStream in=new BufferedInputStream(fin);
		BufferedOutputStream out=new BufferedOutputStream(fout);
		int b;
		long start=System.currentTimeMillis();
		while((b=in.read())!=-1){
			out.write(b);
		}
		long cost=(System.currentTimeMillis()-start)/1000;
		System.out.println("旧I/O(使用缓冲)耗时:"+cost+"s");
		out.close();
		in.close();
	}
	
	public void copyFileNew(File from,File to) throws IOException{
		//使用Channel和Buffer处理
		FileChannel fin=new FileInputStream(from).getChannel();
		FileChannel fout=new FileOutputStream(to).getChannel();
		long start=System.currentTimeMillis();
		ByteBuffer bfi=fin.map(FileChannel.MapMode.READ_ONLY, 0, from.length());
		fout.write(bfi);
		long cost=(System.currentTimeMillis()-start)/1000;
		System.out.println("新I/O耗时:"+cost+"s");
		fout.close();
		fin.close();
	
	}
	
	public static void main(String[] args) throws IOException {
		//复制的文件大一点会更好地体现效果
		new CopyFileCompara().copyFileOld(new File("F:\\01第一讲上.wmv"), new File("F:\\副本1.wmv"));
		new CopyFileCompara().copyFileNew(new File("F:\\01第一讲上.wmv"), new File("F:\\副本2.wmv"));
	}
}

比较java新旧I/O的性能——以复制大文件为例