Java文件下載怎么實(shí)現(xiàn)的

下載就很簡單了

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把你要下載的文件做成超級鏈接，可以不用任何組件

比如說

下載一個(gè)word文檔

a href="名稱.doc"名稱.doc/a

路徑你自己寫

import java.io.File;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.io.RandomAccessFile;

import java.net.HttpURLConnection;

import java.net.ProtocolException;

import java.net.URI;

import java.net.URL;

import java.util.Random;

/**

*

* 實(shí)現(xiàn)了下載的功能*/

public class SimpleTh {

public static void main(String[] args){

// TODO Auto-generated method stub

//String path = "倩女幽魂.mp3";//MP3下載的地址

String path ="";

try {

new SimpleTh().download(path, 3); //對象調(diào)用下載的方法

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

public static String getFilename(String path){//獲得文件的名字

return path.substring(path.lastIndexOf('/')+1);

}

public void download(String path,int threadsize) throws Exception//下載的方法

{//參數(shù) 下載地址，線程數(shù)量

URL url = new URL(path);

HttpURLConnection conn = (HttpURLConnection)url.openConnection();//獲取HttpURLConnection對象

conn.setRequestMethod("GET");//設(shè)置請求格式，這里是GET格式

conn.setReadTimeout(5*1000);//

int filelength = conn.getContentLength();//獲取要下載文件的長度

String filename = getFilename(path);

File saveFile = new File(filename);

RandomAccessFile accessFile = new RandomAccessFile(saveFile, "rwd");

accessFile.setLength(filelength);

accessFile.close();

int block = filelength%threadsize ==0?filelength/threadsize:filelength/threadsize+1;

for(int threadid = 0;threadid=threadsize;threadid++){

new DownloadThread(url,saveFile,block,threadid).start();

}

}

private final class DownloadThread extends Thread{

private URL url;

private File saveFile;

private int block;//每條線程下載的長度

private int threadid;//線程id

public DownloadThread(URL url,File saveFile,int block,int threadid){

this.url = url;

this.saveFile= saveFile;

this.block = block;

this.threadid = threadid;

}

@Override

public void run() {

//計(jì)算開始位置的公式：線程id*每條線程下載的數(shù)據(jù)長度=？

//計(jì)算結(jié)束位置的公式：（線程id+1）*每條線程下載數(shù)據(jù)長度-1=？

int startposition = threadid*block;

int endposition = (threadid+1)*block-1;

try {

try {

RandomAccessFile accessFile = new RandomAccessFile(saveFile, "rwd");

accessFile.seek(startposition);//設(shè)置從什么位置寫入數(shù)據(jù)

HttpURLConnection conn = (HttpURLConnection)url.openConnection();

conn.setRequestMethod("GET");

conn.setReadTimeout(5*1000);

conn.setRequestProperty("Range","bytes= "+startposition+"-"+endposition);

InputStream inStream = conn.getInputStream();

byte[]buffer = new byte[1024];

int len = 0;

while((len = inStream.read(buffer))!=-1){

accessFile.write(buffer, 0, len);

}

inStream.close();

accessFile.close();

System.out.println("線程id："+threadid+"下載完成");

} catch (FileNotFoundException e) {

e.printStackTrace();

}

} catch (IOException e) {

e.printStackTrace();

}

}

}

}

怎樣下載Java源代碼

你下載JDK，里面帶src.zip就是源代碼

但這是JAVA類庫代碼，不是虛擬機(jī)代碼

java se的全部源代碼哪里下載？

如果你已經(jīng)安裝了jdk的話，直接找到j(luò)dk的安裝目錄。有2個(gè)文件一個(gè)是jdk1.6(版本號) 一個(gè)是jre6（Java運(yùn)行環(huán)境） 。進(jìn)入jdk1.6文件夾下，找到src.zip的壓縮文件，解壓就是java se的源代碼