java - 自定义类: Custom type cannot be converted to other custom type

Question

我被分配了两个给定类的作业，一个是抽象父类 Lot.java，另一个是测试类 TestLots.java。我不应该编辑其中任何一个。任务是创建Lot的两个子类，使TestLots中的错误不再是错误。

该程序的目的是按如下顺序显示地 block 的名称和面积:

    Lot ID L3 has area: 13500.0 
    Lot ID L2 has area: 27000.0 
    Lot ID L1 has area: 35000.0 
    Lot ID L4 has area: 70000.0

但是我收到错误:不兼容的类型:LotType1 无法转换为 Lot，并且LotType2 无法转换为 Lot。我怀疑问题出在我的子类以及它应该覆盖或引用父类的方式中。

这是 TestLots，我在其中收到错误:

    public class TestLots {

        public static void main(String args[]){  
            // an array of lots -- some of type1, some of type2
            Lot[] lots = {new LotType1("L1",350, 200), // error here
                new LotType2("L2",100,270),
                new LotType1("L3",100, 270),
                new LotType2("L4",350,200)
            };

            // sort the lots of mixed types by area (note, you'll have to implement
            // Comparable interface correctly in LotType1 and LotType2 for this to work:
            java.util.Arrays.sort(lots);

            // print out sorted results
            for (Lot lot: lots) {
                System.out.print(lot + " "); 
                System.out.println();
            }
        }
    }

这是 Lot，父类

public abstract class Lot {

    public abstract double calculateArea();
    public abstract String getID();

    @Override
    public String toString() {
        return "Lot ID "+ getID() +" has area: "+ calculateArea();
    }
}

子类几乎相同:

public class LotType1 extends Lot implements Comparable<LotType1>{
    String name;
    int height;
    int width;
    double area;

    public LotType1(String name, int height, int width) {
        this.name = name;
        this.height = height;
        this.width = width;
    }

    public String getID() {
        return name;
    }

    public double calculateArea() {
        return area = ((width * height)/2);
    }

    @Override
    public int compareTo(LotType1 lot) {
        area = ((width * height)/2);
        if(area==lot.area)
        {
            return 0;
        }
        else if(area>lot.area)
        {
            return 1;
        }
        else
        {
            return -1;
        }
    }
}

编辑以添加 LotType2:

public class LotType2 extends Lot implements Comparable<LotType2>{
    String name;
    int height;
    int width;
    double area;

    public LotType2(String name, int height, int width) {
        this.name = name;
        this.height = height;
        this.width = width;
    }

    public String getID() {
        return name;
    }

    public double calculateArea() {
        return area = (width * height);
    }

    @Override
    public int compareTo(LotType2 lot) {
        area = (width * height);
        if(area==lot.area)
        {
            return 0;
        }
        else if(area>lot.area)
        {
            return 1;
        }
        else
        {
            return -1;
        }
    }
}

抱歉这篇文章太长了。我决定包含所有相关文件，以防有帮助。

Answer 1

问题是您无法对同一集合中具有不同可比较实现的对象进行排序。更改子类以实现 Comparable of Lot :

    public class LotType1 extends Lot implements Comparable<Lot> {

并在compareTo方法中使用calculateArea():

    @Override
    public int compareTo(Lot lot) {
        if (calculateArea() == lot.calculateArea()) {
            return 0;
        } else if (calculateArea() > lot.calculateArea()) {
            return 1;
        } else {
            return -1;
        }
    }