Swing图形绘制（长方形、椭圆、同心圆及直方图）

ackage example;

import java.awt.Graphics;

//Fig. 5.27: ShapesTest.java, modified by pandenghuang@163.com
//Test application that displays class Shapes.
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import java.awt.Graphics; //handle the display

public class ShapesTest
{

public static class Shapes extends JPanel
{
private int choice; // user's choice of which shape to draw

// constructor sets the user's choice
public Shapes(int userChoice)
{
choice = userChoice;
}

// draws a cascade of shapes starting from the top-left corner
public void paintComponent(Graphics g)
{
super.paintComponent(g);
int width = getWidth(); // total width
int height = getHeight(); // total height
int barHorizontalDistance=width/11;
int barVerticalDistance=height/11;

for (int i = 0; i < 10; i++)
{
// pick the shape based on the user's choice
switch (choice)
{
case 1: // draw rectangles
g.drawRect(10 + i * 10, 10 + i * 10,
50 + i * 10, 50 + i * 10);
break;
case 2: // draw ovals
g.drawOval(10 + i * 10, 10 + i * 10,
50 + i * 10, 50 + i * 10);
break;
case 3: // draw concentric circles
g.drawOval(width/2-(i+1)*10, height/2-(i+1)*10,
10+20*i,  10+20*i);
break;
case 4: // draw bar chart
g.drawRect(i * barHorizontalDistance, height - i * barVerticalDistance,
20, height + i * height/11);
break;
}
}
}
}
public static void main(String[] args)
{
// obtain user's choice
String input = JOptionPane.showInputDialog(
"输入1画长方形\n" +
"输入2画圆形\n"+
"输入3画同心圆\n"+
"输入4画条形图");

int choice = Integer.parseInt(input); // convert input to int

// create the panel with the user's input
Shapes panel = new Shapes(choice);

JFrame application = new JFrame(); // creates a new JFrame

application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
application.add(panel);
application.setSize(300, 300);
application.setVisible(true);
}
} // end class ShapesTest