Java - 如何以多种方式对对象进行排序：Arrays.sort（），Comparable< T> [英] Java - how to sort object in many ways: Arrays.sort(), Comparable<T>

问题描述

假设我有一个包含对象的数组，我有一些员工（对象）。它们都有： int age ，双倍薪水。我想对这个数组进行排序，以便我的类实现 Comparable< Employee> 。我做了一个方法：

Let's say that I have an array with objects, where I have some employees (objects). They all have: int age, double salary. I want to sort this array so my class implements Comparable <Employee>. I've made a method:

public int compareTo(Employee other) {
    return Double.compare(salary, other.salary);
}

没关系，排序工作正常。但我按双薪排序。现在我想按 int age 排序那么现在呢？我做了一个方法：

And it's ok, sorting is working fine. But I'm sorting by double salary. Now I want to sort by int age so what now? I've made a method:

public int compareAge(Employee other) {
    return Integer.compare(age, other.age);
}

我怎样才能使用 Arrays.sort（） 有这个吗？我希望有可能使用这两种方法 - 按工资排序，按年龄排序。感谢您的帮助。

And how can I use Arrays.sort() with this? I want to have possibility to use both methods - sort by salary, sort by age. Thank you for help.

推荐答案

实现多种方式对 Employee 引用，你应该创建单独的类来实现 Comparator< Employee> 。所以你可能有：

To implement multiple ways of sorting a collection of Employee references, you should create separate classes implementing Comparator<Employee>. So you might have:

public class EmployeeAgeComparator implements Comparator<Employee> {
    ...
}

public class EmployeeSalaryComparator implements Comparator<Employee> {
    ...
}

然后你只需传递一个实例适当的比较器进入 Arrays.sort 方法。

Then you just pass an instance of the appropriate comparator into the Arrays.sort method.

基本上，实现可比较是好的 - 但是比较器允许你将被比较的东西与进行比较的东西分开。

Basically, implementing Comparable is good when there's one sort order which is a sensible default - but comparators allow you to separate "the things being compared" from "the thing doing the comparing."

作为旁注，使用 double 来表示货币值（如工资）是一个坏主意，因为二进制浮点的工作方式（例如不能准确地表示0.1）...使用 BigDecimal ，或者存储整数分数（或者你正在使用的任何货币单位）。

As a side-note, using double to represent currency values (like salaries) is a bad idea, due to the way binary floating point works (e.g. not being able to represent 0.1 exactly)... use BigDecimal, or store an integer number of cents (or whatever currency unit you're using).

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