Java 案例代码：从基础到高级354

Java是一种面向对象的编程语言，以其跨平台性、安全性和健壮性而闻名。本篇文章将展示一系列Java案例代码，从初学者到高级程序员，涵盖了各种概念和应用场景。

初学者案例

1. Hello World```java
public class HelloWorld {
public static void main(String[] args) {
("Hello, World!");
}
}
```

2. 变量和数据类型```java
int age = 25;
double salary = 100000.0;
String name = "John Doe";
```

3. 条件语句```java
if (age >= 18) {
("您已成年！");
} else {
("您还未成年！");
}
```

中级案例

4. 循环```java
for (int i = 0; i < 10; i++) {
(i);
}
```

5. 集合```java
List names = new ArrayList();
("John");
("Mary");
("Bob");
```

6. 面向对象编程```java
public class Person {
private String name;
private int age;
public Person(String name, int age) {
= name;
= age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
}
```

高级案例

7. 多线程```java
public class MyThread extends Thread {
@Override
public void run() {
("这是多线程！");
}
}
```

8. 数据库连接```java
Connection connection = ("jdbc:mysql://localhost:3306/my_database", "root", "password");
```

9. RESTful API```java
@GetMapping("/api/users")
public List getAllUsers() {
return ();
}
```

10. Spring Boot```java
@SpringBootApplication
public class MyApp {
public static void main(String[] args) {
(, args);
}
}
```

11. Java 8 Lambda```java
List names = ("John", "Mary", "Bob");
(name -> (name));
```

12. Java 11 Local-Variable Type Inference```java
var names = ("John", "Mary", "Bob");
```

13. Java 12 Text Blocks```java
String html = """


Hello, World!





""";
```

14. Java 13 Switch Expressions```java
String result = switch (dayOfWeek) {
case MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY -> "工作日";
case SATURDAY, SUNDAY -> "周末";
default -> "无效的日期";
};
```

15. Java 14 Records```java
record Person(String name, int age) {}
```

2024-10-31

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