多态
Java中的多态是指同一个方法在不同的对象上有不同的行为:
案例一
以下有四个类 : 动物类与狗、猫类 Test测试类
// 动物类
class Animal {public void sound() {System.out.println("动物发出声音");}
}// 狗类
class Dog extends Animal {@Overridepublic void sound() {System.out.println("狗发出汪汪的声音");}
}// 猫类
class Cat extends Animal {@Overridepublic void sound() {System.out.println("猫发出喵喵的声音");}
}// 测试类
public class PolymorphismExample {public static void main(String[] args) {Animal animal1 = new Dog(); // 父类引用指向子类对象Animal animal2 = new Cat(); // 父类引用指向子类对象animal1.sound(); // 调用的是子类Dog的sound()方法animal2.sound(); // 调用的是子类Cat的sound()方法}
}以上程序会输出:
狗发出汪汪的声音
猫发出喵喵的声音
案例二
以下有四个类 : 车类与宝马、奔驰子类 Test测试类
// 车类
class Car {public void drive() {System.out.println("开车");}
}// 宝马类
class BMW extends Car {@Overridepublic void drive() {System.out.println("开宝马");}
}// 奔驰类
class Benz extends Car {@Overridepublic void drive() {System.out.println("开奔驰");}
}// 测试类
public class PolymorphismExample {public static void main(String[] args) {Car car1 = new BMW(); // 父类引用指向子类对象Car car2 = new Benz(); // 父类引用指向子类对象car1.drive(); // 调用的是子类BMW的drive()方法car2.drive(); // 调用的是子类Benz的drive()方法}
}以上程序会输出:
开宝马
开奔驰
案例三
abstract class Animal {public abstract void move();
}class Cat extends Animal {@Overridepublic void move() {System.out.println("Cat is walking");}
}class Dog extends Animal {@Overridepublic void move() {System.out.println("Dog is running");}
}class Bird extends Animal {@Overridepublic void move() {System.out.println("Bird is flying");}
}public class PolymorphismExample {public static void main(String[] args) {Animal cat = new Cat();Animal dog = new Dog();Animal bird = new Bird();cat.move(); // output: Cat is walkingdog.move(); // output: Dog is runningbird.move(); // output: Bird is flying}
}抽象类
抽象类是指不能实例化的类，只能作为其他类的基类来使用。下面是一些Java抽象类的案例以及答案：
案例一
Shape（形状）抽象类：
abstract class Shape {public abstract double calculateArea();public abstract double calculatePerimeter();
}class Rectangle extends Shape {private double length;private double width;public Rectangle(double length, double width) {this.length = length;this.width = width;}public double calculateArea() {return length * width;}public double calculatePerimeter() {return 2 * (length + width);}
}class Circle extends Shape {private double radius;public Circle(double radius) {this.radius = radius;}public double calculateArea() {return Math.PI * radius * radius;}public double calculatePerimeter() {return 2 * Math.PI * radius;}
}public class Main {public static void main(String[] args) {Shape rectangle = new Rectangle(5, 4);System.out.println("Rectangle Area: " + rectangle.calculateArea());System.out.println("Rectangle Perimeter: " + rectangle.calculatePerimeter());Shape circle = new Circle(3);System.out.println("Circle Area: " + circle.calculateArea());System.out.println("Circle Perimeter: " + circle.calculatePerimeter());}
}以上程序输出结果为：
Rectangle Area: 20.0
Rectangle Perimeter: 18.0
Circle Area: 28.274333882308138
Circle Perimeter: 18.84955592153876
案例二
Animal（动物）抽象类：
abstract class Animal {private String name;public Animal(String name) {this.name = name;}public abstract void sound();public void eat() {System.out.println(name + " is eating.");}
}class Dog extends Animal {public Dog(String name) {super(name);}public void sound() {System.out.println("Dog barks.");}
}class Cat extends Animal {public Cat(String name) {super(name);}public void sound() {System.out.println("Cat meows.");}
}public class Main {public static void main(String[] args) {Animal dog = new Dog("Tom");dog.sound();dog.eat();Animal cat = new Cat("Jerry");cat.sound();cat.eat();}
}输出结果：
Dog barks.
Tom is eating.
Cat meows.
Jerry is eating.
案例三
一个抽象类 `Animal` 和两个继承类 `Dog` 和 `Cat` 的用法。
abstract class Animal {private String name;public Animal(String name) {this.name = name;}public String getName() {return name;}public abstract void makeSound();
}class Dog extends Animal {public Dog(String name) {super(name);}public void makeSound() {System.out.println(getName() + " is barking.");}
}class Cat extends Animal {public Cat(String name) {super(name);}public void makeSound() {System.out.println(getName() + " is meowing.");}
}public class Main {public static void main(String[] args) {Animal dog = new Dog("Tom");dog.makeSound();Animal cat = new Cat("Jerry");cat.makeSound();}
}输出结果：
Tom is barking.
Jerry is meowing.
接口
接口定义了一系列方法的签名（方法名、参数列表和返回类型），而具体的实现则由实现该接口的类来完成
案例一
一个接口 `Drawable` 和两个实现类 `Circle` 和 `Rectangle` 的用法。
interface Drawable {void draw();
}class Circle implements Drawable {public void draw() {System.out.println("Drawing a circle.");}
}class Rectangle implements Drawable {public void draw() {System.out.println("Drawing a rectangle.");}
}public class Main {public static void main(String[] args) {Drawable circle = new Circle();circle.draw();Drawable rectangle = new Rectangle();rectangle.draw();}
}输出结果：
Drawing a circle.
Drawing a rectangle.
案例二
定义一个"动物"的接口，具有"吃"和"睡"两个方法。具体的动物类可以根据需要来实现这个接口，并实现自己独特的行为。
// 定义动物接口
interface Animal {void eat();void sleep();
}// 实现动物接口的猫类
class Cat implements Animal {@Overridepublic void eat() {System.out.println("猫正在吃饭");}@Overridepublic void sleep() {System.out.println("猫正在睡觉");}
}// 实现动物接口的狗类
class Dog implements Animal {@Overridepublic void eat() {System.out.println("狗正在吃骨头");}@Overridepublic void sleep() {System.out.println("狗正在打盹");}
}// 测试类
public class Main {public static void main(String[] args) {Animal cat = new Cat();Animal dog = new Dog();cat.eat(); // 输出：猫正在吃饭cat.sleep(); // 输出：猫正在睡觉dog.eat(); // 输出：狗正在吃骨头dog.sleep(); // 输出：狗正在打盹}
}好,以上内容就是今天学习内容的案例 !!!
