Java多态向上转型和向下转型及优点总结

class Animal{
    public String name;
    public int age;

    public Animal(String name,int age){
        this.name = name;
        this.age = age;
    }

    // 父类中的this是当前对象的引用
    public void eat(){
        System.out.println(this.name + " ");
    }
}

class Dog extends Animal{

    public Dog(String name,int age){
        super(name,age);// 调用父类的构造方法进行从父类继承过来的成员的构造
    }
    public void back(){
        System.out.println(this.name + "汪汪汪 ");
    }
}
public class test {
    public static void main(String[] args) {  
        // 向上转型
        Animal animal = new Dog("小白",3);
        animal.eat();// 调用父类自己的eat
    }
}

public final void eat(){
     // ...
}

class Shape {
    public void draw() {
        System.out.println("画图");
    }
}

class Rect extends Shape {
    @Override
    public void draw() {
        System.out.println("⬜");
    }
}

class Cycle extends Shape {
    @Override
    public void draw() {
        System.out.println("⚪");
    }
}

class Flower extends Shape {
    @Override
    public void draw() {
        System.out.println("❀");
    }
}

class Test2 {
    public static void drawShapes() {
        Rect rect = new Rect();
        Cycle cycle = new Cycle();
        Flower flower = new Flower();
        String[] shapes = {"cycle","rect","cycle","rect","flower"};

        for(String shape : shapes) {
            if(shape.equals("cycle")) {
                cycle.draw();
            }else if (shape.equals("rect")) {
                rect.draw();
            }else{
                flower.draw();
            }
        }
    }

    public static void main(String[] args) {
        drawShapes();
    }
}

public static void main(String[] args){
       Shape shapes = {new Cycle(),new Rect(),new Cycle(),new Rext(),new Flower()};
       // 向上转型
       
       for(Shape shape : shapes){
             shape.draw();
       }
}

class Flower extends Shape{
    public void draw(){
        System.out.println("花!");
    }
}