java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

以下是GeometricObject及其子类Triangle和Circle的Java代码实现：

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 double getArea();
    
    public abstract double getPerimeter();
    
}

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

public class Circle extends GeometricObject {
    private double radius;
    
    public Circle() {
        super();
        this.radius = 1.0;
    }
    
    public Circle(double radius) {
        super();
        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;
    }
}

GeometricObject类具有颜色、是否填充和创建日期等属性，并且定义了抽象方法getArea和getPerimeter计算面积和周长。Triangle和Circle都继承了GeometricObject，并实现了抽象方法getArea和getPerimeter。Triangle还具有三边长的属性，而Circle具有半径的属性。