.idea/.gitignore

@@ -0,0 +1,3 @@
+# 默认忽略的文件
+/shelf/
+/workspace.xml

.idea/misc.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

.idea/modules.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/lesson2.iml" filepath="$PROJECT_DIR$/lesson2.iml" />
+    </modules>
+  </component>
+</project>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>

Calculator.java

@@ -0,0 +1,81 @@
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
+import javax.script.ScriptException;
+
+public class Calculator extends JFrame implements ActionListener {
+    private JTextField display;
+    private StringBuilder input;
+    public Calculator() {
+        input = new StringBuilder();
+        display = new JTextField();
+        display.setEditable(false);
+        display.setFont(new Font("Arial", Font.BOLD, 32));
+        display.setHorizontalAlignment(JTextField.RIGHT);
+        display.setBackground(Color.LIGHT_GRAY);
+        JPanel panel = new JPanel();
+        panel.setLayout(new GridLayout(5, 4, 10, 10)); // Increase number of rows
+        panel.setBackground(Color.GRAY);
+        String[] buttons = {
+                "7", "8", "9", "/",
+                "4", "5", "6", "*",
+                "1", "2", "3", "-",
+                "C", "0", ".", "+", // Add decimal point
+                "<-", "=", "" // Add delete button
+        };
+        for (String text : buttons) {
+            JButton button = new JButton(text);
+            button.setFont(new Font("Arial", Font.PLAIN, 24));
+            button.addActionListener(this);
+            button.setBackground(Color.WHITE);
+            panel.add(button);
+        }
+        add(display, BorderLayout.NORTH);
+        add(panel, BorderLayout.CENTER);
+        setTitle("Calculator");
+        setSize(400, 500);
+        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        setLocationRelativeTo(null);
+    }
+
+    public void actionPerformed(ActionEvent e) {
+        String command = e.getActionCommand();
+
+        if (command.charAt(0) == 'C') {
+            input.setLength(0);
+            display.setText("");
+        } else if (command.equals("<-")) { // Delete the last character
+            if (input.length() > 0) {
+                input.setLength(input.length() - 1);
+                display.setText(input.toString());
+            }
+        } else if (command.charAt(0) == '=') {
+            try {
+                double result = evaluate(input.toString());
+                display.setText(String.valueOf(result));
+                input.setLength(0);
+            } catch (ScriptException ex) {
+                display.setText("Error");
+                input.setLength(0);
+            }
+        } else {
+            input.append(command);
+            display.setText(input.toString());
+        }
+    }
+
+    private double evaluate(String expression) throws ScriptException {
+        ScriptEngine engine = new ScriptEngineManager().getEngineByName("JavaScript");
+        return ((Number) engine.eval(expression)).doubleValue();
+    }
+
+    public static void main(String[] args) {
+        SwingUtilities.invokeLater(() -> {
+            Calculator calculator = new Calculator();
+            calculator.setVisible(true);
+        });
+    }
+}

README.md

@@ -1,2 +0,0 @@
-# lesson2
-

lesson2.iml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

out/production/lesson2/.idea/.gitignore

@@ -0,0 +1,3 @@
+# 默认忽略的文件
+/shelf/
+/workspace.xml

out/production/lesson2/.idea/misc.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

out/production/lesson2/.idea/modules.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/lesson2.iml" filepath="$PROJECT_DIR$/lesson2.iml" />
+    </modules>
+  </component>
+</project>

out/production/lesson2/.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>

out/production/lesson2/lesson2.iml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$" isTestSource="false" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>