class Calculator

package java8;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;

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

public class Calculator extends JFrame{//프레임 상속

	JPanel panel;
	JTextField tField;
	JButton[] buttons; //버튼 배열
	String[] labels={
			"Backspace", "","", "CE", "C",
			"7", "8","9","/", "sqrt",
			"4","5","6", "x","%",
			"1","2","3","-","1/x",
			"0","+/-", ".","+", "="
	};
	
	public Calculator() {
		tField=new JTextField(35);//텍스트입력상자(글자수)
		panel=new JPanel();
		tField.setText("0.");//텍스트값 설정
		//getText() 텍스트 읽기, setText("텍스트") 텍스트 쓰기
		tField.setEditable(false);//입력 불가능 상탱
		//0행, 5열, x축, y축 간격
		panel.setLayout(new GridLayout(0,  5, 3, 3));
		buttons=new JButton[25];
		int index=0;
		for(int rows=0; rows<5; rows++){
			for(int cols=0; cols<5; cols++){
				buttons[index]=new JButton(labels[index]); //버튼 생성
				if(cols>=3)
					buttons[index].setForeground(Color.red);//전경색
				else
					buttons[index].setForeground(Color.blue);
				buttons[index].setBackground(Color.yellow);
				panel.add(buttons[index]);
				index++;
			}
		}
		
		add(tField, BorderLayout.NORTH );
		add(panel, BorderLayout.CENTER);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		pack();
		setVisible(true);
	}
	
	public static void main(String[] args) {
		new Calculator();
	}
	
}