如何通过多个字段比较对象 [英] How to compare objects by multiple fields

问题描述

假设你有一些对象有几个字段可以通过以下方式进行比较：

  public class Person {
 
 private String firstName; 
 private String lastName; 
 private String age; 
 
 / *构造函数* / 
 
 / *方法* / 
 
} 
  

所以在这个例子中，当你询问：

  a。 compareTo（b）> 0 
  

您可能会询问一个姓氏是否在b之前，或者如果a比b早，等等...

在不增加不必要的杂乱或开销的情况下，什么是最简单的方式来实现这些对象之间的多重比较？

• java.lang.Comparable 界面仅允许一个字段进行比较


• 添加大量比较方法（即 compareByFirstName（）， compareByAge（）等等）在我看来是凌乱的。 / li>
  

那么最好的方法是什么？

解决方案

您可以编写一个比较两个Person对象的比较类，您可以根据需要检查多个字段。您可以在比较器中放入一个变量，告诉它要比较哪个字段，尽管写多个比较器可能会更简单。

Assume you have some objects which have several fields they can be compared by:

public class Person {

    private String firstName;
    private String lastName;
    private String age;

    /* Constructors */

    /* Methods */

}

So in this example, when you ask if:

a.compareTo(b) > 0

you might be asking if a's last name comes before b's, or if a is older than b, etc...

What is the cleanest way to enable multiple comparison between these kinds of objects without adding unnecessary clutter or overhead?

• java.lang.Comparable interface allows comparison by one field only
• Adding numerous compare methods (i.e. compareByFirstName(), compareByAge(), etc...) is cluttered in my opinion.

So what is the best way to go about this?

解决方案

You can write a comparator class which compares two Person objects, and you can examine as many of the fields as you like. You can put in a variable in your comparator that tells it which field to compare to, although it would probably be simpler to just write multiple comparators.

这篇关于如何通过多个字段比较对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！