覆盖equals（）方法以检查共享继承的对象中的维相等性

Question

I've provided all four classes involved in this particular issue for those who might desire them.

The primary issue is found within the main() method, as the last line in the main method throws an error which reads as follows:

method equals in class java.lang.Object cannot be applied to given types;

required: java.lang.Object

found: Box2, Cube2

reason: actual and formal argument lists differ in length.

The operator that you use here cannot be used for the type of value that you are using it for. You are either using the wrong type here, or the the wrong operator.

I believe the issue may stem from my approach in overriding the equals() method (which is located within the Box class) being incorrect.

This is the method which is intended to print the desired output, but is instead returning an error.

Any insight on how I may rewrite this method properly would be highly appreciated, as I am at a loss.

public class TestNew
{
    public static void main(String []args)
    {
          Rectangle2 one = new Rectangle2(5, 20);
          Box2 two = new Box2(4, 4, 4);
          Box2 three = new Box2(4, 10, 5);
          Cube2 four = new Cube2(4);

          showEffectBoth(one);
          showEffectBoth(two);
          showEffectBoth(three);
          showEffectBoth(four);
          System.out.println(equals(two, four));
    }

    public static void showEffectBoth(Rectangle2 r)
    {
        System.out.println(r);
    }
}

public class Rectangle2
{
    // instance variables
    private int length;
    private int width;

    /**
     * Constructor for objects of class rectangle
     */
    public Rectangle2(int l, int w)
    {
        // initialise instance variables
        length = l;
        width = w;
    }

    public int getLength()
    {
        return length;
    }

    public int getWidth()
    {
        return width;
    }

    public String toString()
    {
        return "Rectangle - " + length + " X " + width;
    }
}

public class Box2 extends Rectangle2
{
    // instance variables
    private int height;

    /**
     * Constructor for objects of class box
     */
    public Box2(int l, int w, int h)
    {
        // call superclass
        super(l, w);
        // initialise instance variables
        height = h;
    }

    public int getHeight()
    {
        return height;
    }

    public String equals(Box2 o, Cube2 p)
    {
        if(o.getLength() + o.getWidth() + o.getHeight() ==  p.getLength() * 3)
        {
            return o.toString() + " is the same size as " + p.toString();
        }
        else
        {
            return o.toString() + " is not the same size as " + p.toString();
        }
    }

    public String toString()
    {
        return "Box - " + getLength() + " X " + getWidth() + " X " + height;
    }
}

public class Cube2 extends Box2
{
    /**
     * Constructor for objects of class Cube.
     */
    public Cube2(int l)
    {
        // call superclass
        super(l, l, l);
    }

    public String toString()
    {
        return "Cube - " + getLength() + " X " + getLength() + " X " + getLength();
    }
}

Answer 1

Well, there is no static method named equals() and taking 2 arguments in your TestNew class. That's what the compiler tells you. To be able to call a method, the method must exist.