[자바프로그래밍] 인터페이스, 람다식, 패키지 // 미작성

package event;

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

class MyFrame extends JFrame {
	private JButton button1;
	private JButton button2;
	private JButton button3;
	private JPanel panel;

	public MyFrame() {
		this.setSize(300, 200);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		this.setTitle("이벤트 예제");
		panel = new JPanel();
		button1 = new JButton("노란색");
		button1.addActionListener(new MyListener());
		panel.add(button1);
		button2 = new JButton("핑크색");
		button2.addActionListener(new MyListener());
		panel.add(button2);
		button3 = new JButton("파랑색");
		button3.addActionListener(new MyListener());
		panel.add(button3);
		this.add(panel);
		this.setVisible(true);
	}

	private class MyListener implements ActionListener {
		public void actionPerformed(ActionEvent e) {
			if (e.getSource() == button1) {
				panel.setBackground(Color.YELLOW);
			} else if (e.getSource() == button2) {
				panel.setBackground(Color.PINK);
			} else if (e.getSource() == button3) {
				panel.setBackground(Color.BLUE);
			}
		}

	}
}

public class ChangeBackground {
	public static void main(String[] args) {
		MyFrame t = new MyFrame();
	}
}

인터페이스의 정의

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class KeyPad extends JFrame implements ActionListener {
	private JTextField txt;
	private JPanel panel;
	
	KeyPad() {
		txt = new JTextField(20);
		add(txt, BorderLayout.NORTH);
		panel = new JPanel();
		panel.setLayout(new GridLayout(0, 3));
		add(panel, BorderLayout.CENTER);
		
		for(int i=0; i<=9; i++) {
			JButton btn = new JButton("" + i);
			btn.addActionListener(this);
			btn.setPreferredSize(new Dimension(100, 100));
			panel.add(btn);
			
			pack();
			setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
			setVisible(true);
		}
		
	}
		@Override
		public void actionPerformed(ActionEvent e) {
			String command = e.getActionCommand();
			if(command.charAt(0)== 'C')
				txt.setText("");
			else
				txt.setText(txt.getText() + command);
		}
}