[英]How to sort a array of tuple if the tuple is a pre-defined class without implement comparator in Java
I have a pre-defined tuple class which cannot be modified as follows: 我有一个预定义的元组类,无法将其修改如下:
public class Tuple {
protected String name;
public Tuple(int id, String name) {
this.id = id;
this.name = name;
}
}
I have another class which defines an array of the above tuple: 我有另一个类,它定义上述元组的数组:
public class Stack {
protected ArrayList<Tuple> tupleLst;
public Stack(){
this.tupleLst=new ArrayList<Tuple>(10);
}
}
Then I need to sort the array of tuple in another class: for instance: 然后我需要在另一个类中对元组数组进行排序:例如:
public class Algo {
public static int Sort(Relation r){
}
public static void main(String[] arg){
Algo.Sort();
}
The Relation r is the input array of tuples. 关系r是元组的输入数组。 I have searched online, where I saw many people actually are using Comparators and Collections.sort() to do that. 我在网上搜索过,在那里我看到很多人实际上正在使用Comparators和Collections.sort()来做到这一点。 However, after I tried, I noticed that the Tuple class need to implement comparators in order to sort. 但是,在尝试之后,我注意到Tuple类需要实现比较器才能进行排序。 How can I sort the tuple without changing the first two classes? 如何在不更改前两个类的情况下对元组进行排序? Thank you in advance! 先感谢您!
Although Tuple
cannot be modified, you can implement a Comparator
of your own and then pass it to the Collections.sort()
method (which will do a sort of your collection of tuples based on the comparator rule(s). For example: 尽管无法修改Tuple
,但是您可以实现自己的Comparator
,然后将其传递给Collections.sort()
方法(该方法将根据比较器规则对元组进行某种排序。例如:
Comparator<Tuple> myComparator = new Comparator<Tuple>() {
public int compare(Tuple t1, Tuple t2) {
//the comparison rules go here
}
};
Collections.sort(tupleList, myComparator);
If you use Java8, you can achieve this in a single line: 如果使用Java8,则可以单行实现:
myList.sort((t1, t2) -> { <comparison rules implementation> });
or (thanks to @MarkoTopolnik) 或(由于@MarkoTopolnik)
myList.sort(Comparator.comparing(t -> <<get sort key from t>>)
I think you're confusing two methods. 我认为您在混淆两种方法。 One way is to make your Tuple class implement the Comparable interface. 一种方法是使您的Tuple类实现Comparable接口。 I think this is the one you want to avoid since it seems you don't want to modify the Tuple class. 我认为这是您要避免的一种,因为您似乎不想修改Tuple类。
The other way is to define a new class, whose purpose is to compare two Tuples. 另一种方法是定义一个新类,其目的是比较两个元组。 This is what is called a Comparator. 这就是所谓的比较器。 If you pass your list of Tuples and an instance of this comparator then you can sort your Tuples any way you like without modifying the Tuple class. 如果传递了元组列表和此比较器的实例,则可以在不修改元组类的情况下以任意方式对元组进行排序。
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