백준 10845 : 큐 _ 자바 Java

https://www.acmicpc.net/problem/10845

10845번: 큐

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import java.io.*;
import java.util.*;

public class Main {
	
	static Queue<Integer> qu = new LinkedList<>();
	static int last;
	public static void main(String[] args) throws IOException {

		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int tCase = Integer.parseInt(br.readLine());
		
		for(int i=0; i<tCase; i++) {
			queues(br.readLine());
		}
			
	}
	
	private static void queues(String input) {
		StringTokenizer st = new StringTokenizer(input," ");
		int num=0;
		while(st.hasMoreTokens()) {
			switch(st.nextToken()) {
			case "push" : num=Integer.parseInt(st.nextToken());qu.add(num); last=num;	break;
			case "pop" : 	if(qu.isEmpty()) System.out.println(-1); 
							else System.out.println(qu.poll());	break;
			case "front" : 	if(qu.isEmpty()) System.out.println(-1); 
						   	else System.out.println(qu.peek());	break;
			case "empty" :	if(qu.isEmpty()) System.out.println(1); 
							else System.out.println(0);	break;
			case "back" : 	if(qu.isEmpty()) System.out.println(-1); 
							else System.out.println(last);	break;
			case "size" : System.out.println(qu.size());	break;
			}
		}
		
	}

}