具有可比性的Java排序 [英] Java Sort with Comparable

问题描述

我有一个 Person 对象的 ArrayList . Person (人员)具有 name (名称)， age (年龄)和 height (高度).我的目标是对该 ArrayList< Person> 进行排序.我已经实现了 Comparable< Person> 并定义了 compareTo()，但是当我尝试对其进行排序时，它给了我这个错误:

I have an ArrayList of Person objects. A Person has name, age and height. My goal is to sort this ArrayList<Person>. I have implemented Comparable<Person> and have defined compareTo() but when I try to sort it, it give me this error:

ArrayList类型的sort(Comparator)方法不适用于参数()"

The method sort(Comparator) in the type ArrayList is not applicable for the argument ()"

我的理解是，如果您实现Comparable，然后定义 compareTo ，其他所有事情都会为您神奇地完成.

The way I understand is that if you implement Comparable and then define compareTo everything else is magically done for you.

有人可以解释一下它如何工作以及为什么我会收到此错误吗?

Can some one explain how to this works and why I am getting this error?

推荐答案

在其中添加新元素时，您都可以使用使用 Comparable 接口对元素进行排序的结构:

Either you use a structure which uses the Comparable interface to order its elements when you add a new element inside it :

TreeSet<Person> persons = new TreeSet<>();
Person personOne = ...
Person personTwo = ...
persons.add(personOne);
persons.add(personTwo);

要么使用 List 和 Collections.sort(List< T> list)方法，该方法都将要排序的列表作为参数(存在重载)这种方法，但与您的情况无关):

Either you use a List and the Collections.sort(List<T> list) method which takes as argument the list you want to sort (there is an overload of this method but it is not relevant in your case):

List<Person> persons = new ArrayList<>();
Person personOne = ...
Person personTwo = ...
persons.add(personOne);
persons.add(personTwo);
Collections.sort(persons);

使用 TreeSet ，元素将在添加后立即排序，而使用 List ，则在添加元素时不对元素进行排序.调用 Collections.sort()方法对列表进行排序.

With the TreeSet, the elements are sorted as soon as added and with the List, the elements are not sorted when you add them.
Only, the call to the Collections.sort() method sorts the list.

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