[Java] PriorityQueue

자바 우선순위 큐 

입학년도가 빠른순으로 정렬

새로운 정렬방식을 사용하기위해서는 PriorityQueue를 Comparator<>로 재정의 해야한다!!

 

package me.day14.practice.practice02;

import java.util.Comparator;
import java.util.PriorityQueue;

public class Main {
    public static void main(String[] args) {
        System.out.println("===============================================================================");
        System.out.println("\t\t\t\t우선순위 큐");
        System.out.println("===============================================================================");
        // 우선순위가 존재하는 Queue (힙을 통해 구현)

        PriorityQueue<Student> priorityQueue = new PriorityQueue (new Comparator<Student>() {

            @Override
            public int compare(Student o1, Student o2) {
                if (Integer.parseInt(o1.getStudentNo()) < Integer.parseInt(o2.getStudentNo())){
                    return -1;
                } else if (Integer.parseInt(o1.getStudentNo()) > Integer.parseInt(o2.getStudentNo())) {
                    return 1;
                } else {
                    return 0;
                }
            }

            @Override
            public boolean equals(Object obj) {
                return false;
            }
        }) {

        };
        // PriorityQueue Queue에 원소 추가
        priorityQueue.offer(new Student("20212222", "이순신", 85)); // 입학연도: 2021 + 들어간 순서: 1
        priorityQueue.offer(new Student("20211111", "자바킹", 100)); // 입학연도: 2021 + 들어간 순서: 2
        priorityQueue.offer(new Student("20213333", "이제이", 50)); // 입학연도: 2021 + 들어간 순서: 3
        priorityQueue.offer(new Student("20171234", "이텔리", 80)); // 입학연도: 2017 + 들어간 순서: 4
        priorityQueue.offer(new Student("20045555", "이초잉", 70)); // 입학연도: 2004 + 들어간 순서: 5



        while (!priorityQueue.isEmpty()) {
            Student pollStudent = priorityQueue.poll();
            System.out.println("pollStudent = " + pollStudent);
            System.out.println("priorityQueue = " + priorityQueue);
            System.out.println("priorityQueue.size() = " + priorityQueue.size());
            System.out.println();
        }
        System.out.println();
    }

}

 

출력문

 

===============================================================================
우선순위 큐
===============================================================================
pollStudent = Student{studentNo='20045555', name='이초잉', score=70}
priorityQueue = [Student{studentNo='20171234', name='이텔리', score=80}, Student{studentNo='20211111', name='자바킹', score=100}, Student{studentNo='20213333', name='이제이', score=50}, Student{studentNo='20212222', name='이순신', score=85}]
priorityQueue.size() = 4

pollStudent = Student{studentNo='20171234', name='이텔리', score=80}
priorityQueue = [Student{studentNo='20211111', name='자바킹', score=100}, Student{studentNo='20212222', name='이순신', score=85}, Student{studentNo='20213333', name='이제이', score=50}]
priorityQueue.size() = 3

pollStudent = Student{studentNo='20211111', name='자바킹', score=100}
priorityQueue = [Student{studentNo='20212222', name='이순신', score=85}, Student{studentNo='20213333', name='이제이', score=50}]
priorityQueue.size() = 2

pollStudent = Student{studentNo='20212222', name='이순신', score=85}
priorityQueue = [Student{studentNo='20213333', name='이제이', score=50}]
priorityQueue.size() = 1

pollStudent = Student{studentNo='20213333', name='이제이', score=50}
priorityQueue = []
priorityQueue.size() = 0