Question

对于我的生活，我无法弄清楚这段代码有什么问题，请帮忙。我有三个类，GeometricObject，Octagon，它扩展了GeometricObject和TestOctagon，用于测试Octagon类。当我运行TestOctagon类时，我收到此错误：

Object类型的方法clone（）不可见

这是我的代码：

public abstract class GeometricObject {

    private String color = "white";
    private boolean filled;


    protected GeometricObject() {
    }

    protected GeometricObject(String color, boolean filled) {
        this.color = color;
        this.filled = filled;
    }

    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 abstract double getArea();

    public abstract double getPerimeter();
}

import java.lang.Comparable;
import java.lang.Cloneable;

public class Octagon extends GeometricObject implements Comparable<Octagon>, Cloneable{

    double side;    

    public Octagon() {
    }

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

    public Octagon(double side, String color, boolean filled) {
        this.side = side;
        setColor(color);
        setFilled(filled);
    }

    public double getSide() {
        return side;
    }

    public void setSide(double side) {
        this.side = side;
    }

    public double getArea() {
        return (2+4/Math.sqrt(2))*side*side;
    }

    public double getPerimeter() {
        return 8*side;
    }

    @Override
    public int compareTo(Octagon o) {
        if (getArea() > o.getArea())
            return 1;
        else if (getArea() < o.getArea())
            return -1;
        else
            return 0;
    }

    @Override
    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

public class TestOctagon {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        GeometricObject oc1 = new Octagon(5);
        System.out.println(oc1.getArea());
        System.out.println(oc1.getPerimeter());
        GeometricObject oc2 = (GeometricObject)oc1.clone();

    }

}

Answer 1

唐，请注意，方法Object :: clone（）的访问说明符受到保护。它不能从您的TestOctagon类访问，因为您在GeometriObject（oc1）类型的对象上调用此方法，其中克隆方法仍然受到保护，因为它或它的超类都没有覆盖它。尝试将clone方法从Octagon类移动到GeometriObject类。请保留公共访问说明符。请参阅此示例，了解如何执行此操作http://www.javatpoint.com/object-cloning

Object类型的方法clone（）不可见

1 个答案: