java文件複製

使用普通的按字節讀取，再寫入另一個文件，速度太慢。Java提供的JavaChannel能顯著提升速度（暫時不知道原理）

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

public class FileCopy {
	public static void main(String[] args) {
		String from="e:/Thunder_dl_V7.9.37.4952_setup.1433748298.exe";
		String to="e:/copy/target.exe";
		File fileFrom=new File(from);
		File fileTo=new File(to);
		long start=System.currentTimeMillis();
		//normalCopy(fileFrom,fileTo);
		fastCopy(fileFrom, fileTo);
		long end=System.currentTimeMillis();
		System.out.println("複製文件所用時間是："+(end-start)+"ms");
	}
	
	public static void normalCopy(File fileFrom,File fileTo){
		int b;
		FileInputStream from=null;
		FileOutputStream to=null;
		try {
			from=new FileInputStream(fileFrom);
			to=new FileOutputStream(fileTo);
			while((b=from.read())!=-1){
				to.write(b);
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			System.out.println("沒有找到文件");
			e.printStackTrace();
			System.exit(-1);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			System.out.println("文件複製錯誤");
			e.printStackTrace();
			System.exit(-1);
		} finally {
			try {
				from.close();
				to.close();
			} catch(IOException e){
				e.printStackTrace();
			}
		}

	}
	
	public static void fastCopy(File fileFrom,File fileTo){
		FileInputStream from=null;
		FileOutputStream to=null;
		FileChannel in=null;
		FileChannel out=null;
		try {
			from=new FileInputStream(fileFrom);
			to=new FileOutputStream(fileTo);
			in=from.getChannel();//獲取通道
			out=to.getChannel();//
			in.transferTo(0, in.size(), out);  //java提供的複製方法
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			System.out.println("沒有找到文件");
			e.printStackTrace();
			System.exit(-1);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			System.out.println("文件複製錯誤");
			e.printStackTrace();
			System.exit(-1);
		} finally {
			try {			
				from.close();
				in.close();
				to.close();
				out.close();
			} catch(IOException e){
				e.printStackTrace();
			}
		}

	}
}