[Java] Comparable, Comparator

ComparableとComparatorとは?

使用例

package sort;

public class Employee implements Comparable<Employee>{

	int eno;
	String name;
	String job;
	String boss;

	Employee(int eno, String name, String job, String boss){
		this.eno = eno;
		this.name = name;
		this.job = job;
		this.boss = boss;
	}
	
	@Override
	public int compareTo(Employee o) {
		// String을 compare 할 때
		return this.name.compareTo(o.name);
		// int를 compare 할 때
		// return this.eno - o.eno;
	}

...
	
}

package sort;

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

public class Main {

	public static void main(String[] args) {
		Employee emp1 = new Employee(1, "Seo", "디자인", "보스1", 2800);
		Employee emp2 = new Employee(2, "Kim", "마케팅", "보스2", 3000);
		Employee emp3 = new Employee(3, "Yong", "인사", "보스3", 2500);
		Employee emp4 = new Employee(4, "Hong", "개발", "보스4", 4000);
		Employee emp5 = new Employee(5, "Park", "회계", "보스5", 3500);
		
		ArrayList<Employee> list = new ArrayList<Employee>();
		list.add(emp1);
		list.add(emp2);
		list.add(emp3);
		list.add(emp4);
		list.add(emp5);
		
		// 기존 입력 순서로 출력
		System.out.println("입력 순서: \n" + list);
		// Override로 정해놓은 이름 순서로 정렬
		Collections.sort(list);
		// 정렬 뒤 순서로 출력
		System.out.println("Comparable 순서: \n" + list);
		
		// 익명클래스로 Comparator 구현
		Comparator<Employee> salaryCompare = new Comparator<Employee>() {
			@Override
			public int compare(Employee o1, Employee o2) {
				return o2.salary - o1.salary;
			}
		};
		// Comparator 정렬
		Collections.sort(list, salaryCompare);
		// 정렬 뒤 순서로 출력
		System.out.println("Comparator 순서: \n" + list);
	}
}

出力画面

References