设计抽象类GeometricObject及其子类Triangle和Circle。 GeometricObject类设计要求如下： ■ 一个名为color 的Color类型的私有数据域，表示对象的颜色。 ■ 一个名为filled 的Boolean类型的私有数据域，表示对象是否填充颜色。 ■ 一个名为dateCreated的Date类型的私有数据域，表示对象的创建日期。 ■ 一个无参构造方法。 ■ 一个能创建特定color 和filled 的有参构造方法。 ■ 相关数据域的访问器和修改器。 ■ 两个个名为draw和erase的抽象方法。 ■ 一个名为getArea的抽象方法。 ■ 一个名为getPerimeter的抽象方法。 ■ 重写toString方法。

好的，根据您的要求，我来为您设计这个类及其子类。

import java.util.Date;

public abstract class GeometricObject {
    private String color;
    private boolean filled;
    private Date dateCreated;

    public GeometricObject() {
        this.color = "white";
        this.filled = false;
        this.dateCreated = new Date();
    }

    public GeometricObject(String color, boolean filled) {
        this.color = color;
        this.filled = filled;
        this.dateCreated = new Date();
    }

    public String getColor() {
        return color;
    }

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

    public boolean isFilled() {
        return filled;
    }

    public void setFilled(boolean filled) {
        this.filled = filled;
    }

    public Date getDateCreated() {
        return dateCreated;
    }

    public abstract void draw();

    public abstract void erase();

    public abstract double getArea();

    public abstract double getPerimeter();

    @Override
    public String toString() {
        return "created on " + dateCreated + "\ncolor: " + color + " and filled: " + filled;
    }
}

class Triangle extends GeometricObject {
    private double side1;
    private double side2;
    private double side3;

    public Triangle() {
        super();
        this.side1 = 1.0;
        this.side2 = 1.0;
        this.side3 = 1.0;
    }

    public Triangle(double side1, double side2, double side3) {
        super();
        this.side1 = side1;
        this.side2 = side2;
        this.side3 = side3;
    }

    public Triangle(String color, boolean filled, double side1, double side2, double side3) {
        super(color, filled);
        this.side1 = side1;
        this.side2 = side2;
        this.side3 = side3;
    }

    public double getSide1() {
        return side1;
    }

    public void setSide1(double side1) {
        this.side1 = side1;
    }

    public double getSide2() {
        return side2;
    }

    public void setSide2(double side2) {
        this.side2 = side2;
    }

    public double getSide3() {
        return side3;
    }

    public void setSide3(double side3) {
        this.side3 = side3;
    }

    @Override
    public double getArea() {
        double s = (side1 + side2 + side3) / 2.0;
        return Math.sqrt(s * (s - side1) * (s - side2) * (s - side3));
    }

    @Override
    public double getPerimeter() {
        return side1 + side2 + side3;
    }

    @Override
    public void draw() {
        System.out.println("Drawing a triangle...");
    }

    @Override
    public void erase() {
        System.out.println("Erasing a triangle...");
    }

    @Override
    public String toString() {
        return "Triangle:\n" + super.toString() + "\nside1 = " + side1 + ", side2 = " + side2 + ", side3 = " + side3;
    }
}

class Circle extends GeometricObject {
    private double radius;

    public Circle() {
        super();
        this.radius = 1.0;
    }

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

    public Circle(String color, boolean filled, double radius) {
        super(color, filled);
        this.radius = radius;
    }

    public double getRadius() {
        return radius;
    }

    public void setRadius(double radius) {
        this.radius = radius;
    }

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

    @Override
    public double getPerimeter() {
        return 2.0 * Math.PI * radius;
    }

    @Override
    public void draw() {
        System.out.println("Drawing a circle...");
    }

    @Override
    public void erase() {
        System.out.println("Erasing a circle...");
    }

    @Override
    public String toString() {
        return "Circle:\n" + super.toString() + "\nradius = " + radius;
    }
}

以上就是我为您设计的GeometricObject类及其子类Triangle和Circle。如果您有任何问题或者需要进一步帮助，请随时告诉我。