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큐(Queue)란?

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한쪽 끝에서는 데이터의 삽입만 이루어지고 다른 한쪽 끝에서는 데이터의 삭제만 이루어지는 선형리스트 자료구조이다.

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Queue의 특징

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Queue 사용법

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1. Queue 선언하기

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Queue<Integer> queue = new LinkedList<>();
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2. Queue 값 추가(Enqueue)

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Queue<Integer> queue = new LinkedList<>();\r\nqueue.offer(1); //데이터 삽입\r\nqueue.offer(2);\r\nqueue.add(3);   //데이터 삽입
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\n \n \n \n \n \n \"queue1\"\n \n \n

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offer() 와 add() 메서드는 값을 추가 하는건 똑같지만 add() 는 큐가 꽉 찬경우에 IllegalStateException 예외를 던지고 offer()는 추가 실패를 의미하는 false를 리턴한다.

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3. Queue 값 삭제(Dequeue)

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queue.poll();       // queue에 맨 앞에 있는 값 반환 후 삭제\r\nqueue.remove();     // queue에 맨 앞에 있는 값 반환 후 삭제\r\nqueue.clear();      // queue 전체를 비운다.
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\n \n \n \n \n \n \"queue3\"\n \n \n

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element() 와 peek() 메서드는 맨 앞 데이터를 확인 하는건 같지만 element()는 큐가 비어 있는 경우에
\r\nNoSuchElementException 예외를 발생기키고 peek()는 비어있을 경우에 null을 반환한다.

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Queue 구현 코드

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public class ListQueue<T> {\r\n\r\n    static class Node<T> {\r\n        T data;\r\n        Node<T> next;\r\n\r\n        public Node(T data) {\r\n            this.data = data;\r\n        }\r\n    }\r\n\r\n    private Node<T> head;\r\n\r\n    private boolean isEmpty() {\r\n        return head == null;\r\n    }\r\n\r\n    public T add(T item) {\r\n        Node<T> node = new Node<T>(item);\r\n\r\n        if (isEmpty())\r\n            head = node;\r\n\r\n        head.next = node;\r\n\r\n        return node.data;\r\n    }\r\n\r\n    public T remove() {\r\n        if (isEmpty())\r\n            throw new RuntimeException();\r\n\r\n        T data = head.data;\r\n        head = head.next;\r\n\r\n        return data;\r\n    }\r\n\r\n    public T peek() {\r\n        if (isEmpty())\r\n            throw new RuntimeException();\r\n\r\n        return head.data;\r\n    }\r\n\r\n    public void print() {\r\n        Node<T> node = head;\r\n\r\n        while(node != null) {\r\n            System.out.print(node.data + \" \");\r\n            node = node.next;\r\n        }\r\n        System.out.println();\r\n    }\r\n\r\n    public static void main(String[] args) {\r\n        ListQueue<String> queue = new ListQueue<>();\r\n\r\n        queue.add(\"A\");\r\n        queue.add(\"B\");\r\n        queue.print();\r\n        System.out.println(\"front : \" + queue.peek());\r\n\r\n        queue.remove();\r\n        queue.print();\r\n    }\r\n}
","frontmatter":{"title":"큐(Queue) 개념 및 구현","summary":"JAVA,자료구조","date":"2022.07.15.","categories":["JAVA"],"thumbnail":{"childImageSharp":{"gatsbyImageData":{"layout":"constrained","placeholder":{"fallback":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAJCAYAAAAywQxIAAAACXBIWXMAAA7DAAAOwwHHb6hkAAABjElEQVQoz42ST2vUUBTF3wdwJ7gR3Iuu3bgUP4HgdxAK7roQQVdSXEgF7UJoceXCVf+4bB2s6QiRdkorU/S1dHTMpJmZpskkr8lL8t5PWuk4qAM9cO/lcrjnci9HWGsZxd/9OIybEycp1xVHSU5eVENynPAop7KSKNGUlRlyp4KbMmSp3qEhw1PCGIux/4YdVtBlhbPVZXHNY99PhnMCLO5Oj3nHY/3rIeeFMYZaI2DB8ZDteFQQ0tyy6yn6UYYf5bQPM8Kk4Ec/oxtrgljzvZ8Rq4IoLWj1jolUQRAes9dJKc2fRaLZ3GFvVxL4HUJVcvWJy5XHn7gz94WLDxxuTm9w6+Um4n6Nt40ur5w2YmKFu3PbYCwHvo+U35BSkqYp4iQNkoRS5/ix5tLDNS4/qnPj2ToXJj9yfcrl2pSLmHjPa9fn6XILcW+Z2y820EVFURQMBglKKaqq+n3yGXRpePP5gNl6h1V5xMzqT5a2erzb7vG81kYGiqaXML3S4sOYf4szG5zXf/+z0Gj8Agwdmx6EUk5dAAAAAElFTkSuQmCC"},"images":{"fallback":{"src":"/static/690bfeb6da0f0e56ef25ef5b5b0a60bf/d0c01/queue.png","srcSet":"/static/690bfeb6da0f0e56ef25ef5b5b0a60bf/911d9/queue.png 169w,\n/static/690bfeb6da0f0e56ef25ef5b5b0a60bf/f667d/queue.png 339w,\n/static/690bfeb6da0f0e56ef25ef5b5b0a60bf/d0c01/queue.png 677w","sizes":"(min-width: 677px) 677px, 100vw"},"sources":[{"srcSet":"/static/690bfeb6da0f0e56ef25ef5b5b0a60bf/9c557/queue.webp 169w,\n/static/690bfeb6da0f0e56ef25ef5b5b0a60bf/c83e3/queue.webp 339w,\n/static/690bfeb6da0f0e56ef25ef5b5b0a60bf/4f2f2/queue.webp 677w","type":"image/webp","sizes":"(min-width: 677px) 677px, 100vw"}]},"width":677,"height":291}},"publicURL":"/static/690bfeb6da0f0e56ef25ef5b5b0a60bf/queue.png"}}}}]}},"pageContext":{"slug":"/20220717/queue/"}}, "staticQueryHashes": []}