java 实现一个单线程的资源下载器

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package cn.lruihao.base;

import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.HeadlessException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class SingleThreadDown extends JFrame implements ActionListener {
	private final JPanel panel=new JPanel();
	private final JLabel label1=new JLabel("网络资源的单线程下载：");
	private final JLabel label2=new JLabel("网络资源的网址：");
	JButton StartButton = new JButton("单击开始下载");
	JButton resetButton = new JButton("清空");
	JButton exitButton = new JButton("退出");
	JTextField urlField  = new JTextField(20);

	public SingleThreadDown() {
		panel.setLayout(new FlowLayout()); //布局管理器
		label1.setFont(new Font("雅黑",Font.BOLD,15));
		panel.add(label1);
		panel.add(label2);
		panel.add(urlField);
		panel.add(StartButton);
		panel.add(resetButton);
		panel.add(exitButton);
		setContentPane(panel);
		setSize(400,200);
		setLocation(400,400);
		setVisible(true); //面板可视化，也可以在 main 中通过 JFrame 子类对象调用方法设置
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //默认关闭事件
		StartButton.addActionListener(this);//添加点击事件，传入 ActionListener 对象，由于子类继承了 ActionListener 接口，所以 this
		resetButton.addActionListener(this);
		exitButton.addActionListener(this);
	}

	public void download(String address) throws Exception {
		URL url = new URL(address);
		URLConnection urlcon = url.openConnection();
		urlcon.connect();
		InputStream in=urlcon.getInputStream();//获取的字节流对象
		String filePath = url.getFile();
		int pos=filePath.lastIndexOf("/"); //"/"分割的最后一个串的下标
		String fileName = filePath.substring(pos+1);
		FileOutputStream out = new FileOutputStream("C:\\Users\\李瑞豪、\Desktop\\"+fileName);
		byte[] b = new byte[1024];
		int len=0;
		while((len=in.read(b,0,1024))!=-1) {
			out.write(b,0,len);
		}
		out.close();
		in.close();
		JOptionPane.showMessageDialog(this, "下载完毕");
	}

	@Override
	public void actionPerformed(ActionEvent e) {
		if(e.getSource()==StartButton) {
			if("".equals(urlField.getText())){
				JOptionPane.showMessageDialog(this, "请输入资源地址");
			}
			String url = urlField.getText();
			try {
				download(url);
			} catch (Exception e1) {
				JOptionPane.showMessageDialog(this, "资源地址有误，请检查~");
				e1.printStackTrace();
			}
		}else if(e.getSource()==resetButton) {
			urlField.setText("");
		}else {
			System.exit(0);
		}

	}

	public static void main(String[] args) {
		new SingleThreadDown();

	}

}