백준 - 10845번 큐

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayDeque;
import java.util.Queue;
import java.util.StringTokenizer;

public class Main_10845 {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuilder sb = new StringBuilder();

		int N = Integer.parseInt(br.readLine());// 명령어 수
		
		//대기열 생성(큐 생성)
		Queue<Integer> queue = new ArrayDeque<Integer>();
		/*
		  queue
		  ======================================
out <----                                          <---- in
		  ======================================
		 */
		for (int i = 0; i < N; i++) {
			StringTokenizer tokens = new StringTokenizer(br.readLine());
			switch (tokens.nextToken()) {// push pop size empty front back

				case "push":
					queue.offer(Integer.parseInt(tokens.nextToken()));
					break;
				case "pop":
					break;
				case "size":
					break;
				case "empty":
					break;
				case "front":
					sb.append(queue.peek())
					  .append('\n');
					break;
				case "back":
					break;
			}
		} // 각 명령어 처리

		System.out.println(sb.toString());// 결과 출력

		br.close();
	}// main

}