downloadfilethread.java

该多线程下载工具功能强大

package coursedesign;

import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;

public class DownLoadFileThread extends Thread {

	// 网络地址
	private String URL;

	// 线程下载开始点
	private long startPos;

	// 线程下载结束点
	private long endPos;

	private DownLoadFile down;

	private RandomAccessFile file;

	// 已下载量
	private int readPos = 0;

	// 下载分量
	private int in = 0;

	// 构造器
	public DownLoadFileThread(String URL, long startPos, long endPos,
			String saveURL, DownLoadFile down) throws IOException {

		this.URL = URL;
		this.startPos = startPos;
		this.endPos = endPos;
		this.down = down;
		file = new RandomAccessFile(saveURL, "rw");
		file.seek(startPos);
	}

	public void run() {

		try {
			URL url = new URL(URL);
			URLConnection httpConnection = url.openConnection();
			String sProperty = "bytes=" + startPos + "-";
			httpConnection.setRequestProperty("RANGE", sProperty);

			InputStream input = httpConnection.getInputStream();
			byte[] buf = new byte[1024];
			int offset;
			offset = (int) endPos - (int) startPos;
			if (offset > 1024)
				offset = 1024;

			while (down.getStatus() == 0 && startPos < endPos
					&& (in = input.read(buf, 0, offset)) > 0) {
				if (((int) endPos - (int) startPos) < 1024)
					in = (int) endPos - (int) startPos;

				readPos += in;

				offset = (int) endPos - (int) startPos;
				if (offset > 1024)
					offset = 1024;

				file.write(buf, 0, in);
				startPos += in;

				if (in == -1)
					break;

			}

			file.close();
			input.close();
		} catch (Exception ex) {

		}
	}

	public int getReadPos() {
		return readPos;
	}

	public void setReadPos(int readPos) {
		this.readPos = readPos;
	}

}