java - 有没有办法实现 compareTo 方法来比较任何提供的参数？

Question

编译器说“找不到符号：方法 compareTo(java.lang.Object)”。你能建议这里的错误在哪里吗？

这是代码的一部分：

public class OBTComparable<ObjectType> implements Comparable<OBTComparable>
{
    public OTBComparable leftNode = null;
    public OBTComparable mainNode = null;
    public OBTComparable rightNode = null;
    public ObjectType object = null;

    public OBTComparable(ObjectType requiredObject)
    {
        object = requiredObject;
    }

    @Override
    public int compareTo(OBTComparable other)
    {
        if(object.compareTo(other.object) == 0)
            return 0;
        else 
            if (object.compareTo(other.object) > 0)
                return 1;
            else return -1;
    }
}

Answer 1

您也需要范围ObjectType，Comparable因为委派给：OBTComparable compareTo()ObjectType

如果更改<ObjectType>为 <ObjectType extends Comparable<ObjectType>>，它将编译：

public class OBTComparable<ObjectType extends Comparable<ObjectType>> implements Comparable<OBTComparable>

Answer 2

我认为这是您正在寻找的正确代码（为了清楚起见，我替换ObjectType为T）：

class OBTComparable<T extends Comparable<? super T>> implements Comparable<OBTComparable<T>> {
    public OBTComparable<T> leftNode = null;
    public OBTComparable<T> mainNode = null;
    public OBTComparable<T> rightNode = null;
    public T object = null;

    public OBTComparable(T requiredObject) {
        object = requiredObject;
    }

    @Override
    public int compareTo(OBTComparable<T> other) {
        if (object.compareTo(other.object) == 0) {
            return 0;
        } else if (object.compareTo(other.object) > 0) {
            return 1;
        } else return -1;
    }
}

我在这里改变了什么：

1. OBTComparable 使用类型参数，因此您应该在实现时显示它Comparable。因此，您拥有implements Comparable<OBTComparable<T>>而不是简单地implements Comparable<OBTComparable>.
2. 您在方法中比较了两个对象compareTo，但它们是否具有可比性？为确保满足此要求，您应该编写OBTComparable<T extends Comparable<T>>而不是仅OBTComparable<T>. 然后你会知道你可以打电话compareTo。

Answer 3

ObjectType 也必须实现Comparable<ObjectType>。

如果你这样做，我相信：

public int compareTo(OBTComparable other)
{
    if(object.compareTo(other.object) == 0)
        return 0;
    else 
        if (object.compareTo(other.object) > 0)
            return 1;
        else return -1;
}

可以简化为：

public int compareTo(OBTComparable other)
{
    return object.compareTo(other.object);
}