理解继承

Table

1class Vehicle {
2    // protected 允许子类直接访问此成员
3    protected String brand = "Generic Brand"; 
4    
5    public void honk() {
6        System.out.println("Tuut, tuut!");
7    }
8}
9
10class Car extends Vehicle {
11    public int numberOfDoors = 4;
12
13    public void displayBrand() {
14        // 我们可以直接访问 'brand'，因为它被声明为 protected
15        System.out.println("Vehicle Brand: " + brand);
16    }
17}
18
19public class Main {
20    public static void main(String[] args) {
21        var myCar = new Car();
22        
23        // 访问继承的方法
24        myCar.honk();
25        
26        // 通过子类方法访问继承的字段
27        myCar.displayBrand();
28        
29        // 访问子类特有的字段
30        System.out.println("Doors: " + myCar.numberOfDoors);
31    }
32}

1class Employee {
2    protected String name;
3
4    // 父类构造器需要一个名字
5    public Employee(String name) {
6        this.name = name;
7        System.out.println("Employee constructor called");
8    }
9}
10
11class Manager extends Employee {
12    private int teamSize;
13
14    public Manager(String name, int teamSize) {
15        // 必须是第一行
16        super(name); 
17        this.teamSize = teamSize;
18        System.out.println("Manager constructor called");
19    }
20
21    public void displayInfo() {
22        System.out.println(name + " manages " + teamSize + " people.");
23    }
24}
25
26public class Main {
27    public static void main(String[] args) {
28        var mgr = new Manager("Alice", 5);
29        mgr.displayInfo();
30    }
31}

1class Message {
2    public void print() {
3        System.out.println("Message from Parent");
4    }
5}
6
7class Alert extends Message {
8    public void print() {
9        // 调用父类的 print 方法
10        super.print(); 
11        System.out.println("Additional Alert Info");
12    }
13}
14
15public class Main {
16    public static void main(String[] args) {
17        var alert = new Alert();
18        alert.print();
19    }
20}

1class Animal {
2    void eat() {
3        System.out.println("Eating...");
4    }
5}
6
7class Mammal extends Animal {
8    void breathe() {
9        System.out.println("Breathing...");
10    }
11}
12
13class Dog extends Mammal {
14    void bark() {
15        System.out.println("Woof!");
16    }
17}
18
19public class Main {
20    public static void main(String[] args) {
21        var dog = new Dog();
22        
23        dog.bark();    // 定义在 Dog 中
24        dog.breathe(); // 从 Mammal 继承
25        dog.eat();     // 从 Animal 继承（祖父母）
26    }
27}