第一次demo

Operate.java

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+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.util.function.BiFunction;
+
+public class Operate {
+    private JFrame frame;
+    private JTextField displayField;
+    private double firstNumber = 0;
+    private double secondNumber = 0;
+    private String operator = "";
+    private boolean newNumber = true;
+
+    public static void main(String[] args) {
+        EventQueue.invokeLater(() -> {
+            try {
+                Operate window = new Operate();
+                window.frame.setVisible(true);
+            } catch (Exception e) {
+                e.printStackTrace();
+            }
+        });
+    }
+
+    public Operate() {
+        initialize();
+    }
+
+    private void initialize() {
+        frame = new JFrame("Improved Calculator");
+        frame.setBounds(100, 100, 300, 400);
+        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        frame.getContentPane().setLayout(new BorderLayout());
+        frame.setLocationRelativeTo(null);
+
+        // 显示区域
+        displayField = new JTextField();
+        displayField.setEditable(false);
+        displayField.setFont(new Font("Arial", Font.BOLD, 20));
+        displayField.setHorizontalAlignment(JTextField.RIGHT);
+        frame.getContentPane().add(displayField, BorderLayout.NORTH);
+
+        // 按钮面板
+        JPanel buttonPanel = new JPanel();
+        buttonPanel.setLayout(new GridLayout(5, 4));
+        frame.getContentPane().add(buttonPanel, BorderLayout.CENTER);
+
+        // 数字按钮
+        for (int i = 1; i <= 9; i++) {
+            JButton button = new JButton(Integer.toString(i));
+            button.addActionListener(new ActionListener() {
+                @Override
+                public void actionPerformed(ActionEvent e) {
+                    if (newNumber) {
+                        displayField.setText(e.getActionCommand());
+                        newNumber = false;
+                    } else {
+                        displayField.setText(displayField.getText() + e.getActionCommand());
+                    }
+                }
+            });
+            buttonPanel.add(button);
+            if (i % 3 == 0) buttonPanel.add(new JButton()); // 空位
+        }
+
+        // 添加0按钮
+        JButton buttonZero = new JButton("0");
+        buttonZero.addActionListener(e -> {
+            if (!displayField.getText().equals("0")) {
+                displayField.setText(displayField.getText() + "0");
+            }
+        });
+        buttonPanel.add(buttonZero);
+
+        // 小数点按钮
+        JButton buttonDecimal = new JButton(".");
+        buttonDecimal.addActionListener(e -> {
+            if (!displayField.getText().contains(".")) {
+                displayField.setText(displayField.getText() + ".");
+            }
+        });
+        buttonPanel.add(buttonDecimal);
+
+        // 运算符按钮
+        addOperatorButton(buttonPanel, "+", (a, b) -> a + b);
+        addOperatorButton(buttonPanel, "-", (a, b) -> a - b);
+        addOperatorButton(buttonPanel, "*", (a, b) -> a * b);
+        addOperatorButton(buttonPanel, "/", (a, b) -> {
+            if (b == 0) {
+                JOptionPane.showMessageDialog(frame, "除数不能为0！", "错误", JOptionPane.ERROR_MESSAGE);
+                return Double.NaN;
+            }
+            return a / b;
+        });
+
+        // 清除按钮
+        JButton clearButton = new JButton("C");
+        clearButton.addActionListener(e -> {
+            displayField.setText("");
+            firstNumber = 0;
+            secondNumber = 0;
+            operator = "";
+            newNumber = true;
+        });
+        buttonPanel.add(clearButton);
+
+        // 等于号按钮
+        JButton equalsButton = new JButton("=");
+        equalsButton.addActionListener(e -> calculate());
+        buttonPanel.add(equalsButton);
+
+        // 设置按钮样式
+        setButtonStyle(buttonPanel);
+    }
+
+    private void addOperatorButton(JPanel panel, String op, BiFunction<Double, Double, Double> operation) {
+        JButton button = new JButton(op);
+        button.addActionListener(e -> {
+            firstNumber = Double.parseDouble(displayField.getText());
+            operator = op;
+            // 重置 displayField 的内容
+            displayField.setText("");
+            newNumber = true;
+        });
+        panel.add(button);
+    }
+
+    private void calculate() {
+        secondNumber = Double.parseDouble(displayField.getText());
+        switch (operator) {
+            case "+":
+                displayField.setText(String.valueOf(firstNumber + secondNumber));
+                break;
+            case "-":
+                displayField.setText(String.valueOf(firstNumber - secondNumber));
+                break;
+            case "*":
+                displayField.setText(String.valueOf(firstNumber * secondNumber));
+                break;
+            case "/":
+                if (secondNumber == 0) {
+                    JOptionPane.showMessageDialog(frame, "除数不能为0！", "错误", JOptionPane.ERROR_MESSAGE);
+                    return;
+                }
+                displayField.setText(String.valueOf(firstNumber / secondNumber));
+                break;
+        }
+        newNumber = true;
+    }
+
+    private void setButtonStyle(JPanel panel) {
+        for (Component c : panel.getComponents()) {
+            if (c instanceof JButton) {
+                JButton button = (JButton) c;
+                button.setFont(new Font("Arial", Font.BOLD, 16));
+                button.setBackground(Color.LIGHT_GRAY);
+                button.setForeground(Color.BLACK);
+                button.setBorder(BorderFactory.createLineBorder(Color.DARK_GRAY));
+            }
+        }
+    }
+}