java面向对象编程_包_继承_多态_重载和重写_抽象类_接口_this和super（2）

class Animal{
    protected String name;
    protected int  age;
    public void eat(){
        System.out.println("animal eat()!");
    }
}
class Dog extends Animal{
    protected int height;
    public void running(){
        System.out.println("dog running()!");
    }
}
public class Test_1 {
    public static void main(String[] args) {
        Animal animal = new Animal();
        animal = new Dog();  //1.子类对象赋值给了父类引用
        Animal animal1 = new Dog(); //2.和 1 等价
        animal.eat(); //调用父类中的方法
        //error animal只能访问父类中的字段和方法！
        animal.height=1;
        animal.running();
    }
}

//方法传参
class Animal{
    protected String name;
    protected int  age;
    public void eat(){
        System.out.println("animal eat()!");
    }
}
class Dog extends Animal{
    protected int height;
    public void running(){
        System.out.println("dog running()!");
    }
}
public class Test_2 {
    public static void func(Animal animal){
        animal.eat();
    }
    public static void main(String[] args) {
        Dog dog = new Dog();
        func(dog);
        func(new Dog()); //子类对象赋值给了父类引用！
    }
}

//方法返回
class Animal{
    protected String name;
    protected int  age;
    public void eat(){
        System.out.println("animal eat()!");
    }
}
class Dog extends Animal{
    protected int height;
    public void running(){
        System.out.println("dog running()!");
    }
}
public class Test_2 {
    public static Animal func(){
       return new Dog();  //子类对对象返回给了父类引用！
    }
    public static void main(String[] args) {
       Animal animal = func();
       animal.eat();
    }
}

//运行时绑定
class Animal{
    protected String name;
    protected int  age;
    public void eat(){
        System.out.println("animal eat()!");
    }
}
class Dog extends Animal{
    protected int height;
    @Override
    public void eat() {
        System.out.println("dog eat()!");
    }
    public void running(){
        System.out.println("dog running()!");
    }
}
public class Test_2 {
    public static void main(String[] args) {
       Animal animal = new Dog();
       animal.eat(); //运行时绑定！
    }
}

//类的实现者
class Shape {
    public void draw() {
        // 啥都不用干
    }
}
class Cycle extends Shape {
    @Override
    public void draw() {
        System.out.println("○");
    }
}
class Rect extends Shape {
    @Override
    public void draw() {
        System.out.println("□");
    }
}
class Flower extends Shape {
    @Override
    public void draw() {
        System.out.println("♣");
    }
}
//类的调用者
public class Test_1{
    public static void main(String[] args) {
        Shape shape1 = new Flower();
        Shape shape2 = new Cycle();
        Shape shape3 = new Rect();
        drawShape(shape1);
        drawShape(shape2);
        drawShape(shape3);
    }
    // 打印单个图形
    public static void drawShape(Shape shape) {
        shape.draw();
    }
}

//向下转型
class Animal {
    protected String name;
    public Animal(String name) {
        this.name = name;
    }
    public void eat(String food) {
        System.out.println("我是一只小动物");
        System.out.println(this.name + "正在吃" + food);
    }
}
class Bird extends Animal {
    public Bird(String name) {
        super(name);
    }
    public void eat(String food) {
        System.out.println("我是一只小鸟");
        System.out.println(this.name + "正在吃" + food);
    }
    public void fly() {
        System.out.println(this.name + "正在飞");
    }
}
public class Test_2 {
    public static void main(String[] args) {
        Animal animal = new Bird("鸽鸽"); //先借助向上转型
        animal.eat("脐橙");
        //animal.fly;  //error
        Bird bird;
        bird = (Bird)animal; //向下转型需要强转
        bird.fly();
    }
}

abstract class Shape { 
    abstract public void draw(); 
}

abstract class Shape {
    protected  int longth;
    protected int wide;
    public int area(){
        return longth*wide;
    }
     abstract public  void draw();
}