抽象类中的公共变量

abstract class Shape {
    // 公共实例变量
    public String color;

    // 抽象方法
    public abstract double area();

    // 具体方法
    public void setColor(String color) {
        this.color = color;
    }

    public String getColor() {
        return color;
    }
}

class Circle extends Shape {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    @Override
    public double area() {
        return Math.PI * radius * radius;
    }
}

class Square extends Shape {
    private double side;

    public Square(double side) {
        this.side = side;
    }

    @Override
 public double area() {
        return side * side;
    }
}

public class Main {
    public static void main(String[] args) {
        Circle circle = new Circle(5);
        circle.setColor("Red");
        System.out.println("Circle color: " + circle.getColor());
        System.out.println("Circle area: " + circle.area());

        Square square = new Square(4);
        square.setColor("Blue");
        System.out.println("Square color: " + square.getColor());
        System.out.println("Square area: " + square.area());
    }
}

abstract class Shape {
    private String color;

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    // 其他代码...
}

abstract class Shape {
    public final String color;

    public Shape(String color) {
        this.color = color;
    }

    // 其他代码...
}