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import java.io.bufferedreader; import java.io.file; import java.io.fileinputstream; import java.io.inputstream; import java.io.inputstreamreader; import java.io.randomaccessfile; import java.net.httpurlconnection; import java.net.url; public class mutilethreaddownload { /** * 線程的數(shù)量 */ private static int threadcount = 3; /** * 每個下載區(qū)塊的大小 */ private static long blocksize; /** * 正在運行的線程的數(shù)量 */ private static int runningthreadcount; /** * @param args * @throws exception */ public static void main(string[] args) throws exception { // 服務器文件的路徑 string path = "http://192.168.1.100:8080/ff.exe"; url url = new url(path); httpurlconnection conn = (httpurlconnection) url.openconnection(); conn.setrequestmethod("get"); conn.setconnecttimeout(5000); int code = conn.getresponsecode(); if (code == 200) { long size = conn.getcontentlength();// 得到服務端返回的文件的大小 system.out.println("服務器文件的大小：" + size); blocksize = size / threadcount; // 1.首先在本地創(chuàng)建一個大小跟服務器一模一樣的空白文件。 file file = new file("temp.exe"); randomaccessfile raf = new randomaccessfile(file, "rw"); raf.setlength(size); // 2.開啟若干個子線程分別去下載對應的資源。 runningthreadcount = threadcount; for (int i = 1; i <= threadcount; i++) { long startindex = (i - 1) * blocksize; long endindex = i * blocksize - 1; if (i == threadcount) { // 最后一個線程 endindex = size - 1; } system.out.println("開啟線程：" + i + "下載的位置：" + startindex + "~" + endindex); new downloadthread(path, i, startindex, endindex).start(); } } conn.disconnect(); } private static class downloadthread extends thread { private int threadid; private long startindex; private long endindex; private string path; public downloadthread(string path, int threadid, long startindex, long endindex) { this.path = path; this.threadid = threadid; this.startindex = startindex; this.endindex = endindex; } @override public void run() { try { // 當前線程下載的總大小 int total = 0; file positionfile = new file(threadid + ".txt"); url url = new url(path); httpurlconnection conn = (httpurlconnection) url .openconnection(); conn.setrequestmethod("get"); // 接著從上一次的位置繼續(xù)下載數(shù)據(jù) if (positionfile.exists() && positionfile.length() > 0) {// 判斷是否有記錄 fileinputstream fis = new fileinputstream(positionfile); bufferedreader br = new bufferedreader( new inputstreamreader(fis)); // 獲取當前線程上次下載的總大小是多少 string lasttotalstr = br.readline(); int lasttotal = integer.valueof(lasttotalstr); system.out.println("上次線程" + threadid + "下載的總大小：" + lasttotal); startindex += lasttotal; total += lasttotal;// 加上上次下載的總大小。 fis.close(); } conn.setrequestproperty("range", "bytes=" + startindex + "-" + endindex); conn.setconnecttimeout(5000); int code = conn.getresponsecode(); system.out.println("code=" + code); inputstream is = conn.getinputstream(); file file = new file("temp.exe"); randomaccessfile raf = new randomaccessfile(file, "rw"); // 指定文件開始寫的位置。 raf.seek(startindex); system.out.println("第" + threadid + "個線程：寫文件的開始位置：" + string.valueof(startindex)); int len = 0; byte[] buffer = new byte[512]; while ((len = is.read(buffer)) != -1) { randomaccessfile rf = new randomaccessfile(positionfile, "rwd"); raf.write(buffer, 0, len); total += len; rf.write(string.valueof(total).getbytes()); rf.close(); } is.close(); raf.close(); } catch (exception e) { e.printstacktrace(); } finally { // 只有所有的線程都下載完畢后 才可以刪除記錄文件。 synchronized (mutilethreaddownload.class) { system.out.println("線程" + threadid + "下載完畢了"); runningthreadcount--; if (runningthreadcount < 1) { system.out.println("所有的線程都工作完畢了。刪除臨時記錄的文件"); for (int i = 1; i <= threadcount; i++) { file f = new file(i + ".txt"); system.out.println(f.delete()); } } } } } } } |
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持服務器之家。
