Java-Calculator/JavaCalculator.java at main · aarishahmad/Java-Calculator · GitHub

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import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class JavaCalculator extends JFrame implements ActionListener {
    private final JTextField display = new JTextField();
    private String current = "";
    private String operator = "";
    private double first = 0;

    public JavaCalculator() {
        try { UIManager.setLookAndFeel("javax.swing.plaf.nimbus.NimbusLookAndFeel"); } catch (Exception ignored) {}

        setTitle("Swing Calculator");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(360, 520);
        setLocationRelativeTo(null);
        setLayout(new BorderLayout(10, 10));
        ((JComponent) getContentPane()).setBorder(new EmptyBorder(12, 12, 12, 12));

        JLabel title = new JLabel("Calculator", SwingConstants.LEFT);
        title.setFont(new Font("Segoe UI Semibold", Font.PLAIN, 20));
        add(title, BorderLayout.PAGE_START);

        display.setEditable(false);
        display.setHorizontalAlignment(JTextField.RIGHT);
        display.setFont(new Font("Consolas", Font.PLAIN, 26));
        display.setBorder(BorderFactory.createCompoundBorder(
                BorderFactory.createLineBorder(new Color(70, 70, 70), 1, true),
                new EmptyBorder(8, 10, 8, 10)));
        display.setBackground(new Color(245, 245, 245));
        add(display, BorderLayout.NORTH);

        String[] buttons = {
            "7","8","9","/","C",
            "4","5","6","*","⌫",
            "1","2","3","-","=",
            "0",".","+/-","+","AC"
        };

        JPanel panel = new JPanel(new GridLayout(4, 5, 6, 6));
        panel.setBackground(new Color(245, 245, 245));

        Color numBg = new Color(230, 234, 238);
        Color opBg  = new Color(66, 133, 244);
        Color opFg  = Color.WHITE;

        for (String text : buttons) {
            JButton btn = new JButton(text);
            btn.setFont(new Font("Segoe UI", Font.BOLD, 14));
            btn.setFocusPainted(false);
            btn.setMargin(new Insets(4, 6, 4, 6));
            boolean isOp = "/-*+=C⌫AC+/-".contains(text);
            btn.setBackground(isOp ? opBg : numBg);
            btn.setForeground(isOp ? opFg : Color.DARK_GRAY);
            btn.addActionListener(this);
            panel.add(btn);
        }
        add(panel, BorderLayout.CENTER);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String cmd = ((JButton) e.getSource()).getText();
        switch (cmd) {
            case "C":
                current = "";
                display.setText("");
                break;
            case "AC":
                current = "";
                operator = "";
                first = 0;
                display.setText("");
                break;
            case "⌫":
                if (!current.isEmpty()) {
                    current = current.substring(0, current.length() - 1);
                    display.setText(current);
                }
                break;
            case "+/-":
                if (!current.isEmpty()) {
                    if (current.startsWith("-")) current = current.substring(1);
                    else current = "-" + current;
                    display.setText(current);
                }
                break;
            case "+": case "-": case "*": case "/":
                commitCurrent();
                operator = cmd;
                current = "";
                break;
            case "=":
                commitCurrent();
                operator = "";
                current = String.valueOf(first);
                display.setText(current);
                break;
            default: // digits or dot
                current += cmd;
                display.setText(current);
        }
    }

    private void commitCurrent() {
        if (!current.isEmpty()) {
            double val = Double.parseDouble(current);
            if (operator.isEmpty()) {
                first = val;
            } else {
                first = apply(first, val, operator);
            }
        }
    }

    private double apply(double a, double b, String op) {
        switch (op) {
            case "+": return a + b;
            case "-": return a - b;
            case "*": return a * b;
            case "/": return b == 0 ? 0 : a / b;
            default: return b;
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new JavaCalculator().setVisible(true));
    }
}