多线程复制文件

 要使用多线程复制，必须使用RandomAccessFile类

 

RandomAccessFile是用来访问那些保存数据记录的文件的，这样你就可以用seek( )方法来访问记录，并进行读写了。这些记录的大小不必相同；但是其大小和位置必须是可知的。行为类似存储在文件系统中一个大型的byte[]数组。

RandomAccessFile竟然会是不属于InputStream和OutputStream类系的。

 

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

public class MyThread implements Runnable{

	public String filepath = "";
	public String srcfile="";
	public long startposition;
	public long endposition;
	RandomAccessFile file;
	
	public MyThread(String srcfile,String filepath,long startposition,long endposition){
		this.srcfile = srcfile;
		this.filepath = filepath;
		this.startposition = startposition;
		this.endposition = endposition;
	}
	
	@Override
	public void run() {
		FileInputStream fio = null;
		Thread  thread = Thread.currentThread();
		System.out.println(thread.getId());
		
		try {
			fio = new FileInputStream(this.srcfile);
			byte[] temp = new byte[1024];//1k
			int templength;
			fio.skip((int)this.startposition);
			file = new RandomAccessFile(this.filepath,"rw");
			file.seek((int)this.startposition);
			while((templength = fio.read(temp)) > 0 && this.startposition <= this.endposition){
				file.write(temp,0,templength);
				this.startposition = this.endposition;
			}
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			try {
				fio.close();
				file.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		
		
	}
	
}

 

测试 方法

package com;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class UploadFile {

	public static void main(String[] args) {
		
		FileInputStream fio = null;
		String srcfile="c:\\2013年春节放假通知.docx";
		String targetfile = "c:\\huangbiao.docx";
		
		try {
			fio = new FileInputStream(srcfile);
			long length = fio.available();
			System.out.println(length);
			int tnum = (int) (length%(1024*1024)==0?length/(1024*1024):length/(1024*1024)+1);
			for(int i=0;i<tnum;i++){
				MyThread myThread = null;
				if((length-(i-1)*1024*1024)>0){
					myThread = new MyThread(srcfile,targetfile,i*1024*1024,(i+1)*1024*1024-1);
				}else{
					myThread = new MyThread(srcfile,targetfile,i*1024*1024,length);
				}
				Thread thread = new Thread(myThread);
				thread.start();
			}
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			try {
				fio.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		
		
	}

}