java 如何使用 Comparable 比较链表中的通用节点？
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How to compare generic nodes in a linked list using Comparable?
提问by hash
I am implementing a sorted list using linked lists. My node class looks like this
我正在使用链接列表实现排序列表。我的节点类看起来像这样
public class Node<E>{
E elem;
Node<E> next, previous;
}
In the sorted list class I have the add method, where I need to compare generic objects based on their implementation of compareTo() methods, but I get this syntax error "The method compareTo(E) is undefined for type E". I have tried implemnting the compareTo method in Node, but then I can't call any of object's methods, because E is generic type. Here is the non-finished body of add(E elem) method.
在排序列表类中，我有 add 方法，我需要根据它们对 compareTo() 方法的实现来比较通用对象，但我收到此语法错误“方法 compareTo(E) 未定义为类型 E”。我曾尝试在 Node 中实现 compareTo 方法，但后来我无法调用任何对象的方法，因为 E 是泛型类型。这是 add(E elem) 方法的未完成主体。
public void add(E elem)
{
Node<E> temp = new Node<E>();
temp.elem = elem;
if( isEmpty() ) {
temp.next = head;
head.previous = temp;
head = temp;
counter++;
}else{
for(Node<E> cur = head; cur.next != null ; cur= cur.next) {
**if(temp.elem.comparTo(cur.elem)) {**
//do the sort;
}/*else{
cur.previous = temp;
}*/
}
//else insert at the end
}
}
Here is one of the object implemnting compareTo method
这是实现 compareTo 方法的对象之一
public class Patient implements Comparable<Patient>{
public int compareTo(Patient that)
{
return (this.getPriority() <= that.getPriority() ? 1 : 0 );
}
}
采纳答案by Bohemian
Bound E to Comparable:
将 E 绑定到 Comparable：
public class Node<E extends Comparable<E>>{
E elem;
Node<E> next, previous;
}
It will compile now.
它现在会编译。
回答by Sorrow
It seems that your generic Emust be E extends Comparable<E>. This way you will get the access to the compareTo(E other)method. However, you will be unable to add elements that are not implementing this interface.
看来您的泛型E必须是E extends Comparable<E>. 这样您就可以访问该compareTo(E other)方法。但是，您将无法添加未实现此接口的元素。
回答by Waldheinz
If you want the elements stored in your nodes to be comparable, you can state this using generics:
如果您希望存储在节点中的元素具有可比性，您可以使用泛型来说明这一点：
public class Node<E extends Comparable<E>> {
E elem;
Node<E> next, previous;
}
this way it is sure, that every Eimplements the Comparableinterface, so you can safely call the compareTomethod.
这样可以确定，每个都E实现了Comparable接口，因此您可以安全地调用该compareTo方法。
回答by Dorus
Try
尝试
public class Node<E extends Comparable<E>>{
E elem;
Node<E> next, previous;
}
