1. Java基础语法

1.1 变量声明

int number = 10;
String name = "John Doe";

1.2 数据类型

Java有基本数据类型和引用数据类型。基本数据类型包括int、float、double、char、boolean等。

1.3 运算符

Java支持算术运算符、关系运算符、逻辑运算符等。

2. 面向对象编程

2.1 类和对象

public class Person { private String name; private int age; public Person(String name, int age) { this.name = name; this.age = age; } public void displayInfo() { System.out.println("Name: " + name + ", Age: " + age); }
}

2.2 继承和多态

public class Employee extends Person { private String jobTitle; public Employee(String name, int age, String jobTitle) { super(name, age); this.jobTitle = jobTitle; } public void displayJobTitle() { System.out.println("Job Title: " + jobTitle); }
}

3. 控制结构

3.1 条件语句

int number = 10;
if (number > 5) { System.out.println("Number is greater than 5");
} else { System.out.println("Number is not greater than 5");
}

3.2 循环语句

for (int i = 0; i < 5; i++) { System.out.println("Iteration " + i);
}

4. 集合框架

4.1 List

List list = new ArrayList<>();
list.add("Apple");
list.add("Banana");
list.add("Cherry");

4.2 Set

Set set = new HashSet<>();
set.add("Apple");
set.add("Banana");
set.add("Cherry");

4.3 Map

Map map = new HashMap<>();
map.put("Apple", 1);
map.put("Banana", 2);
map.put("Cherry", 3);

5. 异常处理

5.1 try-catch

try { int result = 10 / 0;
} catch (ArithmeticException e) { System.out.println("Cannot divide by zero");
}

6. Java 8新特性

6.1 Lambda表达式

List list = Arrays.asList("Apple", "Banana", "Cherry");
list.forEach(name -> System.out.println(name));

6.2 Stream API

List list = Arrays.asList("Apple", "Banana", "Cherry");
list.stream().filter(name -> name.startsWith("A")).forEach(System.out::println);

7. Java Web开发

7.1 Servlet

@WebServlet("/hello")
public class HelloServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.getWriter().println("Hello, World!"); }
}

7.2 JSP

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

 

 
Hello, World!

8. Java并发编程

8.1 线程

public class MyThread extends Thread { public void run() { System.out.println("Thread is running"); }
}
public class Main { public static void main(String[] args) { MyThread thread = new MyThread(); thread.start(); }
}

8.2 同步

public class Counter { private int count = 0; public synchronized void increment() { count++; }
}

9. Java数据库连接

9.1 JDBC

public class Main { public static void main(String[] args) { try { Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "username", "password"); Statement statement = connection.createStatement(); ResultSet resultSet = statement.executeQuery("SELECT * FROM users"); while (resultSet.next()) { System.out.println(resultSet.getString("name")); } } catch (SQLException e) { e.printStackTrace(); } }
}

10. Java性能优化

10.1 内存泄漏

public class MemoryLeakExample { private static List