學習Java10

簡單的GUI:

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class Day implements ActionListener{
	
	JFrame frame;

	public static void main(String[] args){
		Day gui =new Day();
		gui.go();
	}
	public void go(){
	JFrame frame=new JFrame();
	frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	
	JButton button=new JButton("Change!");
	button.addActionListener(this);
		
		MyDrawPanel drawPanel= new MyDrawPanel();
		
		frame.getContentPane().add(BorderLayout.SOUTH,button);
		frame.getContentPane().add(BorderLayout.CENTER,drawPanel);
		frame.setSize(300,300);
		frame.setVisible(true);
		}
	public void actionPerformed(ActionEvent event){
	frame.repaint();
	}
	
}
class MyDrawPanel extends JPanel{
	public void paintComponent(Graphics g){
	Graphics2D g2d =(Graphics2D) g;
	int red= (int) (Math.random()*255);
	int green= (int) (Math.random()*255);
	int blue= (int) (Math.random()*255);
	Color startColor=new Color(red,green,blue);
	
     red= (int) (Math.random()*255);
	 green= (int) (Math.random()*255);
     blue= (int) (Math.random()*255);
	 Color endColor=new Color(red,green,blue);
	 
	 GradientPaint gradient= new GradientPaint(70,70,startColor,150,150,endColor);
	 g2d.setPaint(gradient);
	 g2d.fillOval(70,70,100,100);
	 }
	}