Question

import java.lang.Math;

public class FiguraProba
{

  public abstract class Figura {
    public abstract double pole();
    public abstract double obwod();
  }

  public abstract class Czworokat extends Figura {
    public double obwod(double bok1, double bok2, double bok3, double bok4)
    {
        return (bok1+bok2+bok3+bok4);
    }

    public abstract double pole();
  }

  public class Kwadrat extends Czworokat {

    double bok1;

    public Kwadrat(double bokPodany)
    {
        bok1=bokPodany;
    }

    public double pole(double bok1) {
        return bok1*bok1;
    }
  }

  public class Prostokat extends Czworokat {

    double bok1, bok2;

    public Prostokat(double bokPodany1, double bokPodany2)
    {
        bok1=bokPodany1;
        bok2=bokPodany2;
    }
    public double pole(double bok1, double bok2) {
        return bok1*bok2;
    }
  }

  public static void main(String args[] )
  {
    //System.out.println(Math.sin(90*(Math.PI/180)));
  }
}

我为我的英语道歉并使用英文变量名称。我的目标是：我有对象f.e squareExample with side 5.我想调用函数从类square计算区域并从类quadrange调用函数周长来计算周长。可能吗？ Compilator说：＆＃34; FiguraProba.Prostokat不是抽象的，并且不会在FiguraProba.Czworokat中抽象抽象方法pole（）。＆＃34;我理解错误，但我不知道如何解决错误以实现目标。

很抱歉使用外语代码变量和类。以下是所有单词的含义： figura - 图 kwadrat - square czworokat - 四边形 prostokat - 矩形杆区 obwod - 周长 bok - side

Answer 1

解决方案如下：

import java.lang.Math;

public class FiguraProba
{

  public abstract class Figura {

    public abstract double pole();
    public abstract double obwod();
  }

  public abstract class Czworokat extends Figura {
    public double obwod(double bok1, double bok2, double bok3, double bok4)
    {
        return (bok1+bok2+bok3+bok4);
    }

    public abstract double pole();
  }

  public class Kwadrat extends Czworokat {

    double bok1;
    public Kwadrat(double bokPodany)
    {
        bok1=bokPodany;
    }

    // Method without any arguments like the Figura class
    // When you extend an abstract class, you have to 
    // implement the exact method with the exact number of arguments
    // Of course you are obligated only if you can create an instance 
    // of that object. The perfect example when you are not obligated to 
    // implement a method is class Czworokat. Czworokat is not 
    // obligated, because you can not create an instance out of it.
    public double pole() {
        return bok1*bok1;
    }
  }

  public class Prostokat extends Czworokat {
    double bok1, bok2;

    public Prostokat(double bokPodany1, double bokPodany2)
    {
        bok1=bokPodany1;
        bok2=bokPodany2;
    }

    // Same logic applies here.
    // When you extend an abstract class, you have to 
    // implement the exact method with the exact number of arguments
    // Of course you are obligated only if you can create an instance 
    // of that object. The perfect example when you are not obligated to 
    // implement a method is class Czworokat. Czworokat is not 
    // obligated, because you can not create an instance out of it.
    public double pole() {
        return bok1*bok2;
    }
  }

  public static void main(String args[] )
  {
    //System.out.println(Math.sin(90*(Math.PI/180)));
  }
}

如果您只使用类属性并代表它返回值，那么这就是您想要的。如果你确实希望pole方法带有一个和两个参数（就像你在代码中那样），那么你仍然需要删除抽象的pole方法，或者你需要实现那个确切的方法ZERO论点。

你不能通过不实施没有参数的pole来违反合同。如果您需要更深入地了解abstract类，那么我建议您查看官方Java documentation。

Answer 2

如果要覆盖抽象类中的方法，则必须在界面中将它看起来像它。所以你的方法应该有相同的名称和相同的参数。

在其他世界中，你有一个带有签名双极（double bok1）的方法，但你仍然需要覆盖方法dobule pole（）;

抽象类，继承，用数字编程的最佳方法

2 个答案: