Java Comparator

上代码：

package co.young.ComparatorExample;

import java.util.Arrays;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;
import java.util.Comparator;

public class ComparableExample {
    public static void main(String[] args) {
        Employee[] staff =  new Employee[3];
        staff[0] =  new Employee( "harry Hacker" , 35000 );
        staff[1] =  new Employee( "carl cracke" , 75000 );
        staff[2] =  new Employee( "tony Tester" , 38000 );
        Arrays.sort(staff);

        System.out.println("As Arrays: ");
        for (Employee e: staff)
            System.out.println(e.toString());

        ArrayList<Employee> staffList = new ArrayList<>();
        staffList.add(new Employee( "harry Hacker" , 35000 ));
        staffList.add(new Employee( "carl cracke" , 75000 ));
        staffList.add(new Employee( "tony Tester" , 38000 ));
        Collections.sort(staffList, new CustomComparator());

        System.out.println("As ArrayList: ");
        for (Employee e: staffList) {
            System.out.println(e.toString());
        }
    }
}

class Employee implements Comparable<Employee> {
    private int id;
    private String name;
    private double salary;

    public Employee(String name, double salary) {
        this.name = name;
        this.salary = salary;
        Random ID =  new Random();
        id = ID.nextInt(10000000);
    }
    public int getId() {
        return id;
    }
    public String getName() {
        return name;
    }
    public double getSalary() {
        return salary;
    }

    public int compareTo(Employee other) {
        if (salary < other.salary)
            return - 1 ;
        if (salary > other.salary)
            return 1 ;
        return 0 ;
    }

    @Override
    public String toString() {
        return "id=" + getId() + "  name=" + getName() + ".salary=" + getSalary();
    }
}

class CustomComparator implements Comparator<Employee> {
    @Override
    public int compare(Employee e1, Employee e2) {
        return e1.compareTo(e2);
    }
}

输出：

As Arrays:
id = 187862  name = "harry Hacker" salary = 35000.0
id = 4744557  name = "tony Tester" salary = 38000.0
id = 2432769  name = "carl cracke" salary = 75000.0
As ArrayList:
id = 9443980  name = "harry Hacker" salary = 35000.0
id = 6015335  name = "tony Tester" salary = 38000.0
id = 9993145  name = "carl cracke" salary = 75000.0