如何正确使用Java比较器？ [英] How to use Java comparator properly?

问题描述

如果我有以下课程：

public class Employee {
    private int empId;
    private String name;
    private int age;

    public Employee(int empId, String name, int age) {
        // set values on attributes
    }
    // getters & setters
}

我如何使用按名称比较的比较器，然后是年龄，然后是id ？

How can I use comparator that compares by name, then age, then id?

推荐答案

您需要实现它，以便按首选元素排序。也就是说，您需要按名称进行比较，然后如果该比较相等，则按年龄等进行比较。下面列出了一个示例：

You need to implement it so that it orders by preferred elements. That is, you need to compare by name, then if that comparison is equal, compare by age, etc. An example is listed below:

public class EmployeeComparator implements Comparator<Employee> {

  @Override
  public int compare(Employee e1, Employee e2) {
    int nameDiff = e1.getName().compareTo(e2.getName());

    if(nameDiff != 0) {
      return nameDiff;
    }

    int ageDiff = e1.getAge() - e2.getAge();

    if(ageDiff != 0) {
      return ageDiff;
    }

    int idDiff = e1.getEmpId() - e2.getEmpId();

    return idDiff;
  }
}

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