자바 다 중 스 레 드 정지점 다운로드 실현

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 { 
  /** 
   *       
   */ 
  private static int threadCount = 3; 
 
  /** 
   *           
   */ 
  private static long blocksize; 
 
  /** 
   *            
   */ 
  private static int runningThreadCount; 
 
  /** 
   * @param args 
   * @throws Exception 
   */ 
  public static void main(String[] args) throws Exception { 
    //          
    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();//               
      System.out.println("        ：" + size); 
      blocksize = size / threadCount; 
      // 1.                        。 
      File file = new File("temp.exe"); 
      RandomAccessFile raf = new RandomAccessFile(file, "rw"); 
      raf.setLength(size); 
      // 2.                  。 
      runningThreadCount = threadCount; 
      for (int i = 1; i <= threadCount; i++) { 
        long startIndex = (i - 1) * blocksize; 
        long endIndex = i * blocksize - 1; 
        if (i == threadCount) { 
          //        
          endIndex = size - 1; 
        } 
        System.out.println("    ：" + i + "     ：" + 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 { 
        //            
        int total = 0; 
        File positionFile = new File(threadId + ".txt"); 
        URL url = new URL(path); 
        HttpURLConnection conn = (HttpURLConnection) url 
            .openConnection(); 
        conn.setRequestMethod("GET"); 
        //                 
        if (positionFile.exists() && positionFile.length() > 0) {//         
          FileInputStream fis = new FileInputStream(positionFile); 
          BufferedReader br = new BufferedReader( 
              new InputStreamReader(fis)); 
          //                   
          String lasttotalstr = br.readLine(); 
          int lastTotal = Integer.valueOf(lasttotalstr); 
          System.out.println("    " + threadId + "      ：" 
              + lastTotal); 
          startIndex += lastTotal; 
          total += lastTotal;//           。 
          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"); 
        //           。 
        raf.seek(startIndex); 
        System.out.println(" " + threadId + "   ：        ：" 
            + 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 { 
        //                        。 
        synchronized (MutileThreadDownload.class) { 
          System.out.println("  " + threadId + "     "); 
          runningThreadCount--; 
          if (runningThreadCount < 1) { 
            System.out.println("           。         "); 
            for (int i = 1; i <= threadCount; i++) { 
              File f = new File(i + ".txt"); 
              System.out.println(f.delete()); 
            } 
          } 
        } 
 
      } 
    } 
  } 
}