DownloadFile.java

package test.utils;import java.io.BufferedReader;import java.io.File;import java.io.FileReader;import java.io.IOException;import java.io.RandomAccessFile;import java.io.UnsupportedEncodingException;import java.net.HttpURLConnection;import java.net.URL;import java.net.URLDecoder;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;/** * java 多執行緒下載檔案 */public class DownloadFile {	public static void main(String[] args) {		DownloadFile df = new DownloadFile();		try {			List<String> urlList = new ArrayList<String>();			df.readFileByLines("f:\\Download\\url.txt", urlList);			int l = urlList.size();			for (int i = 0; i < l; i++) {				df.download(urlList.get(i), "f:\\Download");			}		} catch (Exception e) {			e.printStackTrace();		}	}		/**	 * 下載檔案	 * @param urlStr	 * @param dirStr	 */	public void download(String urlStr, String dirStr) {		RandomAccessFile osf = null;		File dir = new File(dirStr);		dir.mkdirs();		try {			String fileName = dirStr + "\\" + getFileName(urlStr);			File ff = new File(fileName);			if (ff.exists()) {				ff.delete();			}			System.out.println(fileName + ":::" + urlStr);			URL url = new URL(urlStr);			HttpURLConnection http = (HttpURLConnection) url.openConnection();			if (404 == http.getResponseCode()) {				System.out.println(urlStr + "下載失敗，下載的檔案不存在");				return;			}			int httpLen = http.getContentLength();			int tn = 5;//設定5個執行緒下載一個檔案			int len = httpLen / tn;// 捨去餘數計算每個執行緒應下載平均長度,最後一個執行緒再加上餘數,則是整個檔案的長度			File f = new File(fileName);			if (f.exists()) {				f.delete();				osf = new RandomAccessFile(f, "rw");				osf.seek(httpLen - 1);				osf.write(0);			} else {				osf = new RandomAccessFile(f, "rw");				osf.seek(httpLen - 1);				osf.write(0);			}			int bn = 0;// 每個執行緒寫入檔案的位元組數			for (int j = 0; j < tn; j++) {				if (j == tn - 1) {//最後一個執行緒加上餘數長度位元組					bn = len + (httpLen % tn);				} else {					bn = len;				}				Thread t = new DownloadThread(j, urlStr, fileName, len * j, bn);				t.start();			}		} catch (Exception e) {			e.printStackTrace();			System.out.println("error:" + urlStr);		} finally {			if (null != osf) {				try {					osf.close();				} catch (IOException e) {					e.printStackTrace();				}			}		}	}	/**	 * 獲取檔名	 * @param url	 * @return String	 * @throws UnsupportedEncodingException	 */	public String getFileName(String url) throws UnsupportedEncodingException {		String a = URLDecoder.decode(url, "utf-8");		int s = a.lastIndexOf("/") + 1;		int e = a.lastIndexOf("?");		if (e > -1) {			return a.substring(s, e);		}		String fileName = a.substring(s);		System.out.println(fileName);		return fileName;	}	/**	 * 讀下載地址檔案	 * @param fileName	 * @param urlList	 */	private void readFileByLines(String fileName, List<String> urlList) {		File file = new File(fileName);		BufferedReader reader = null;		StringBuilder sb = new StringBuilder();		Map<String, String> m = new HashMap<String, String>();		try {			System.out.println("以行為單位讀取檔案內容，一次讀一整行：");			reader = new BufferedReader(new FileReader(file));			// reader = new BufferedReader(new InputStreamReader(new			// FileInputStream(fileName),"ISO-8859-1"));			String tempString = null;			// 一次讀入一行，直到讀入null為檔案結束			while ((tempString = reader.readLine()) != null) {				sb.append(tempString);				if (!m.containsKey(tempString)) {					urlList.add(tempString);					m.put(tempString, "");				}			}			System.out.println(urlList.size());			reader.close();		} catch (IOException e) {			e.printStackTrace();		} finally {			if (reader != null) {				try {					reader.close();				} catch (IOException e1) {					e1.printStackTrace();				}			}		}	}}

DownloadThread.java

package test.utils;import java.io.File;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.io.RandomAccessFile;import java.math.BigDecimal;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;public class DownloadThread extends Thread {	String httpUrl;	int start;	int end;	String fileName;	RandomAccessFile osf;	boolean f = false;	public DownloadThread(int i, String httpUrl, String fileName, int start, int end) {		this.setName("t" + i); // 子執行緒名稱		this.httpUrl = httpUrl; // 下載地址		this.fileName = fileName;		this.start = start; // 子執行緒讀取/寫入起始位元組		this.end = end;// 子執行緒寫入結束位元組長度	}	public void run() {		try {			osf = new RandomAccessFile(fileName, "rw");			URL url = new URL(httpUrl);			HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();			httpURLConnection.setRequestProperty("User-Agent", "download");// 自定義ua,可以模擬任何瀏覽器			httpURLConnection.setRequestProperty("RANGE", "bytes=" + start + "-");// 設定斷點位置,向伺服器請求從檔案哪個位元組開始讀取			osf.seek(start);// 設定檔案從哪個位元組開始寫入			InputStream input = httpURLConnection.getInputStream();			int cacheSize = 2048;			byte b[] = new byte[cacheSize];// 設定緩衝池,每次只讀2048位元組			int l = 0;// 計算子執行緒讀取和寫入檔案長度,當長度大於每個子執行緒平均下載長度則終止執行緒			int c = 0;//			System.out.println(this.getName()+" 開始下載。。。");//			Date startDate=new Date();//子執行緒開始下載時間			double fff = -1;			while ((c = input.read(b, 0, cacheSize)) != -1 && (l <= end)) {// 執行緒下載位元組長度控制誤差小於緩衝池大小				osf.write(b, 0, c);				b = new byte[cacheSize];// 重新初始化,避免讀入舊資料				l += c;				double f = ((double) l / (double) end);				BigDecimal bg = new BigDecimal(f);				double f1 = bg.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();				double fa = f1 * 100;				if (fa > fff) {					System.out.println(this.getName() + "---" + fileName + ":   " + fa + "%");					fff = fa;				}				if (fa >= 100) {					break;				}			}			System.out.println(this.getName() + "---" + fileName + " finish");//			Date endDate=new Date();//子執行緒結束下載時間//			System.out.println(this.getName()+" 執行緒耗時： "+(endDate.getTime()-startDate.getTime())/1000+" 秒,實際共下載："+l+ "位元組");// 子執行緒下載耗時（秒）		} catch (FileNotFoundException e1) {			System.out.println(fileName);			f = true;		} catch (MalformedURLException e) {			e.printStackTrace();		} catch (IOException e) {			e.printStackTrace();		} finally {			if (null != osf) {				try {					osf.close();				} catch (IOException e) {					e.printStackTrace();				}			}			if (f) {				File f = new File(fileName);				f.delete();			}		}	}}