▶ 윈도우로 계산기를 만들어 보자 package com.simple.gui; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JTextField; public class CalcUI extends JFrame implements ActionListener{ JLabel lblNum1; JLabel lblNum2; JLabel lblResult; JTextField tfNum1; JTextField tfNum2; JTextField tfResult..