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import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

public class Ex2_1 extends JApplet implements ActionListener {

public static JButton btn;

public static JPanel pnl;

public static JDialog dlg;

public static int num;

public static JTextField txtNum;

public static JButton btnEnter;

public static JButton btnCancel;

public Ex2_1(){

super();

btn = new JButton("draw spiral");

pnl = new JPanel();

pnl.setBackground(Color.YELLOW);

this.setLayout(new BorderLayout());

add("North", btn);

add("Center",pnl);

btn.addActionListener(this);

this.setSize(300, 330);

setVisible(true);

}

public void actionPerformed(ActionEvent event){

JButton btn = (JButton)event.getSource();

if(btn.getText().equals("draw spiral")){

dlg = new JDialog();

txtNum = new JTextField(20);

btnEnter = new JButton("确定");

btnCancel = new JButton("取消");

dlg.setLayout(new FlowLayout());

dlg.setTitle("输入");

dlg.add(new JLabel("Enter the winding number"));

dlg.add(txtNum);

dlg.add(btnEnter);

dlg.add(btnCancel);

btnEnter.addActionListener(this);

btnCancel.addActionListener(this);

dlg.setVisible(true);

dlg.setSize(250, 150);

dlg.setResizable(false);

}

else{

if(btn.getText().equals("确定")){

num = Integer.parseInt(txtNum.getText().trim());

dlg.dispose();

draw();

}

else if(btn.getText().equals("取消")){

dlg.dispose();

}

}

}

public void draw(){

Graphics g = pnl.getGraphics();

pnl.update(g);

int CX = 150, CY = 150; //原点坐标

double multiple; //倍数

double n;

int x1, y1, x2, y2;

multiple = 150.0 / num;

x1 = (int)(0*Math.cos(2*Math.PI*0)*multiple)+150;

y1 = (int)(0*Math.sin(2*Math.PI*0)*multiple)+150;

for(n=0.001; n

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