问题描述

好的，这是一个棘手的问题.我有一个集合列表.我想按顺序对集合中的对象进行排序.

Ok this is a tricky one. I have a list of Sets. I would like to sort the objects in the Sets in an order.

将每个集合想象成代表学校的一个班级.每个集合都包含人员对象.一个人对象持有一个字符串值作为名称.我想在循环并写出之前按名称排列 Set 中的 Persons.

Imagine each set as repressenting a class in a school. Each set contains person objects. A person object holds a String value for name. I'd like to arrange the Persons in the Set by name before I loop through and write them out.

有没有办法使用 Collections.sort(); 或类似的东西来实现这一点?

Is there anywahy to use Collections.sort(); or something similar to achieve this?

for (Set<Person> s : listOfAllChildren) {       
      for (Person p : s) {
        if(p.getClass().equalsIgnoreCase("Jones")){
          System.out.println(p.getName());
          }
         else if...//carry on through other classes 
        }                              
      }        

我知道一个班有 2 个以上的孩子可能有相同的名字，但请忽略这个

推荐答案

一个 Set 没有 ordering 的概念，因为它是一个集合.

A Set has no notion of ordering because, well, it's a set.

TreeSet 类实现的SortedSet 接口可以使用.只需向构造函数提供适当的 Comparator，或让您的 Person 类实现 Comparable.

There is a SortedSet interface implemented by TreeSet class that you can use. Simply provide an appropriate Comparator to the constructor, or let your Person class implements Comparable.