Java抽象类Abstract Class示例代码详解

abstract class 类名 {
    // 可以包含成员变量、构造方法、具体方法和抽象方法
    abstract void 抽象方法名(); // 抽象方法没有方法体
}

abstract class Animal {
    // 抽象方法：所有动物必须实现的接口
    public abstract void makeSound();
    // 具体方法：所有动物共享的行为
    public void sleep() {
        System.out.println("This animal is sleeping.");
    }
}

abstract class Shape {
    // 公共方法：计算面积的默认实现（可被子类覆盖）
    public abstract double area();
    // 具体方法：打印形状信息
    public void displayInfo() {
        System.out.println("Shape with area: " + area());
    }
}

abstract class Employee {
    protected String name;
    protected int id;
    public Employee(String name, int id) {
        this.name = name;
        this.id = id;
    }
    public abstract double computePay();
}

Animal myDog = new Dog(); // Dog是Animal的子类
myDog.makeSound(); // 调用Dog类的实现

abstract class Shape {
    abstract double area();
}
class Circle extends Shape {
    private double radius;
    public Circle(double radius) { this.radius = radius; }
    @Override
    double area() { return Math.PI * radius * radius; }
}
class Rectangle extends Shape {
    private double width, height;
    public Rectangle(double width, double height) { 
        this.width = width; this.height = height; 
    }
    @Override
    double area() { return width * height; }
}

abstract class ReportTemplate {
    public void generateReport() {
        collectData();
        formatData();
        printReport();
    }
    abstract void collectData();
    abstract void formatData();
    void printReport() {
        System.out.println("Printing report...");
    }
}

abstract class DatabaseConnection {
    public abstract void connect();
    public abstract void disconnect();
}

// 抽象类：定义动物的公共行为
abstract class Animal {
    protected String name;
    public Animal(String name) {
        this.name = name;
    }
    // 抽象方法：子类必须实现
    public abstract void makeSound();
    // 具体方法：所有动物共享
    public void sleep() {
        System.out.println(name + " is sleeping.");
    }
}

// 具体类：Dog实现Animal的抽象方法
class Dog extends Animal {
    public Dog(String name) {
        super(name);
    }
    @Override
    public void makeSound() {
        System.out.println(name + " says: Woof!");
    }
}
// 具体类：Cat实现Animal的抽象方法
class Cat extends Animal {
    public Cat(String name) {
        super(name);
    }
    @Override
    public void makeSound() {
        System.out.println(name + " says: Meow!");
    }
}

public class Main {
    public static void main(String[] args) {
        // 通过多态调用抽象类方法
        Animal myDog = new Dog("Buddy");
        Animal myCat = new Cat("Whiskers");
        myDog.makeSound(); // 输出: Buddy says: Woof!
        myDog.sleep();     // 输出: Buddy is sleeping.
        myCat.makeSound(); // 输出: Whiskers says: Meow!
        myCat.sleep();     // 输出: Whiskers is sleeping.
    }
}