一、需求
假設現在有個如此的需求:需要對一個這樣的僱員列表進行排序,排序規則如下:
1、首先級別最高的排在前面,
2、如果級別相等,那麼按工資排序,工資高的排在前面,
3、如果工資相當則按入職年數排序,入職時間最長的排在前面。
僱員對象包含級別、工資和入職年份,代碼如下:
package com.lyz.sort.bean;
import java.io.Serializable;
/**
* 僱員信息
* @author liuyazhuang
*
*/
public class Employee implements Serializable {
private static final long serialVersionUID = 4775629632953317597L;
/**
* ID
*/
public int id;
/**
* 級別
*/
public int level;
/**
* 工資
*/
public int salary;
/**
* 入職年數
*/
public int year;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getLevel() {
return level;
}
public void setLevel(int level) {
this.level = level;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
public int getYear() {
return year;
}
public void setYear(int year) {
this.year = year;
}
public Employee(int id, int level, int salary, int year) {
this.id = id;
this.level = level;
this.salary = salary;
this.year = year;
}
}
二、實現Comparator接口
這裏我們實現Java.util.Comparator接口,用於對僱員列表進行排序,代碼如下:
package com.lyz.sort;
import java.util.Comparator;
import com.lyz.sort.bean.Employee;
/**
* 核心排序類
* @author liuyazhuang
*
*/
public class EmpComparator implements Comparator<Employee> {
@Override
public int compare(Employee employee1, Employee employee2) {
int cr = 0;
//按級別降序排列
int a = employee2.getLevel() - employee1.getLevel();
if (a != 0) {
cr = (a > 0) ? 3 : -1;
} else {
//按薪水降序排列
a = employee2.getSalary() - employee1.getSalary();
if (a != 0) {
cr = (a > 0) ? 2 : -2;
} else {
//按入職年數降序排列
a = employee2.getYear() - employee1.getYear();
if (a != 0) {
cr = (a > 0) ? 1 : -3;
}
}
}
return cr;
}
}
三、驗證排序結果
下面用一個單元測試,來驗證排序結果是否正確
package com.lyz.sort.test;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.junit.Test;
import com.lyz.sort.EmpComparator;
import com.lyz.sort.bean.Employee;
/**
* 測試排序類
*
* @author liuyazhuang
*
*/
public class SortTest {
@Test
public void sortTest() throws Exception {
List<Employee> employeeList = new ArrayList<Employee>() {
{
add(new Employee(1, 9, 10000, 10));
add(new Employee(2, 9, 12000, 7));
add(new Employee(3, 5, 10000, 12));
add(new Employee(4, 5, 10000, 6));
add(new Employee(5, 3, 5000, 3));
add(new Employee(6, 1, 2500, 1));
add(new Employee(7, 5, 8000, 10));
add(new Employee(8, 3, 8000, 2));
add(new Employee(9, 1, 3000, 5));
add(new Employee(10, 1, 2500, 4));
add(new Employee(11, 2, 2000, 4));
}
};
Collections.sort(employeeList, new EmpComparator());
System.out.println("ID\tLevel\tSalary\tYears");
System.out.println("=============================");
for (Employee employee : employeeList) {
System.out.printf("%d\t%d\t%d\t%d\n", employee.getId(), employee.getLevel(), employee.getSalary(),
employee.getYear());
}
System.out.println("=============================");
}
}