相关疑难解决方法(0)

我们来看看Java中的以下简单代码片段.

interface Sum
{
    abstract public void showSum();
}

interface Mul
{
    abstract public void showMul();
}

abstract class Super implements Sum
{
    protected int x;
    protected int y;

    public Super(int x, int y)
    {
        this.x=x;
        this.y=y;
    }

    //No error, though the method showSum() of the implementing iterface Sum is commented. Why?

    /*public void showSum()
    {
        System.out.println("Sum = "+(x+y));
    }*/
}

final class Calculation extends Super implements Mul
{
    public Calculation(int x, int y)
    {
        super(x,y);
    }

    public void showSum() …

interface ICanvasTool
{
    void Motion(Point newLocation);
    void Tick();
}

abstract class CanvasTool_BaseDraw : ICanvasTool
{
    protected abstract void PaintAt(Point location);

    public override void Motion(Point newLocation)
    {
        // implementation
    }
}

class CanvasTool_Spray : CanvasTool_BaseDraw
{
    protected abstract void PaintAt(Point location)
    {
        // implementation
    }

    public override void Tick()
    {
        // implementation
    }
}

这不编译.我可以添加一个抽象方法"Tick_Implementation"到CanvasTool_BaseDraw,然后实现ICanvasTool.Tick在CanvasTool_BaseDraw同一个班轮只是调用Tick_Implementation.这是推荐的解决方法吗？