package yjs;

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

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

public class Calculator extends JFrame{
	private JPanel panel;
	private JTextField display;
	private JButton[] buttons;
	private String[] labels = {"Backspace", "", "", "CE", "C", "7", "8", "9", "/",
								"sqrt", "4", "5", "6", "*", "%", "1", "2", "3", "-", "1/x",
								"0", "-/+", ".", "+", "="};
	private double result = 0;
	private String operator = "=";
	private boolean startOfNumber = true;
	public Calculator(){
		display = new JTextField(35);
		panel = new JPanel();
		display.setText("0.0");
		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]);
				if (cols >= 3)
					buttons[index].setForeground(Color.red);
				else
					buttons[index].setForeground(Color.blue);
				buttons[index].setBackground(Color.yellow);
				panel.add(buttons[index]);
				buttons[index].addActionListener((e)->
				{
					String command = e.getActionCommand();
					if (command.charAt(0) == 'C') {
						startOfNumber = true;
						result = 0;
						operator = "=";
						display.setText("0.0");
					} else if (command.charAt(0) >= '0' && command.charAt(0) <= '9'
							|| command.equals(".")) {
						if (startOfNumber == true)
							display.setText(command);
						else
							display.setText(display.getText() + command);
						startOfNumber = false;
					} else {
						if (startOfNumber) {
							if (command.equals("-")) {
								display.setText(command);
								startOfNumber = false;
							} else
								operator = command;
						} else {
							double x = Double.parseDouble(display.getText());
							calculate(x);
							operator = command;
							startOfNumber = true;
						}
					}
				});
				index++;
			}
		}
		add(display, BorderLayout.NORTH);
		add(panel, BorderLayout.CENTER);
		setVisible(true);
		pack();
	}

private void calculate(double n) {
	if (operator.equals("+"))
		result += n;
	else if (operator.equals("-"))
		result -= n;
	else if (operator.equals("*"))
		result *= n;
	else if (operator.equals("/"))
		result /= n;
	else if (operator.equals("="))
		result = n;
	display.setText("" + result);
}
public static void main(String args[]) {
	Calculator s = new Calculator();
}
}