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

//  雙向隊列類
public class Deque {
 private LinkedList list = new LinkedList();
 public void putFirst(Object v) { list.addFirst(v); }
 public void putLast(Object v) { list.addLast(v); }
 public Object getFirst() {
  return list.removeFirst();
 }
 public Object getLast() {
  return list.removeLast();
 }
 public boolean isEmpty() {
  return list.isEmpty();
 }
}

// 主函數運行
class dequework {
 public static void main(String[] args) throws IOException{
  Deque deque = new Deque();
  
  String waste;
  int Num;
  String tmp;
 System.out.println("創建一個數字隊列??！\n"); 
 System.out.println("功能鍵如下：\n");  
 System.out.println("前面加入數字請按 '4' \n"); 
 System.out.println("后面加入數字請按 '6' \n"); 
 System.out.println("前面刪除數字請按 '8' \n"); 
 System.out.println("后面刪除數字請按 '2' \n"); 
 System.out.println("退出請按 '9' \n\n\n"); 
 // 接受功能鍵輸入
 BufferedReader   ar = 
                  new BufferedReader(new InputStreamReader(System.in));
                  System.out.println("請輸入功能鍵:  ");      
                  waste= ar.readLine().toString();
                  Num= Integer.parseInt(waste);
                  ar=null;
                  
while(Num!=9)
  {
  switch(Num)
  {
  	case 4: 
  	         tmp=putin.putinNum();
  	         if(tmp!=null)
  	         {  	      	        
             deque.putFirst(tmp);
             System.out.println("成功從前面加入數字!\n");
             }
             break;            
    case 6:
             tmp=putin.putinNum();
             if(tmp!=null)
             {	        
             deque.putLast(tmp);
             System.out.println("成功從后面加入數字!\n");
             }
             break;             
    case 8:
             if(! deque.isEmpty())
             {
             System.out.println("你從前面刪除的數字為：\n");	        
             System.out.println(deque.getFirst());
             }
             break;                
    case 2:
             if(! deque.isEmpty())
             {
             System.out.println("你從后面刪除的數字為：\n");	        
             System.out.println(deque.getLast());
             }
             else
             {
             System.out.println("隊列為空！請重新輸入！！\n");	
             }
             break;                   

    default:
             System.out.println("輸入不正確！\n");
             break;
 }
 //接受功能鍵輸入
  BufferedReader  cr = 
                  new BufferedReader(new InputStreamReader(System.in));
                  System.out.println("\n請輸入功能鍵:  ");       
                  waste= cr.readLine().toString();
                  System.out.println("\n\n"); 
                  Num= Integer.parseInt(waste);
                  cr=null;
 }
}
}



// 輸入數字函數
class putin {
        
        public static String putinNum() {
        
                int val = 0;
                String tmp = "";
                
                try {
                        
                        System.out.print("\nPlease Input : "); 
                        
                        BufferedReader        br = 
                                new BufferedReader(new InputStreamReader(System.in));
                        
                        tmp = br.readLine().toString();
                        
                        if (putin.isNumber(tmp)) {
                                val = Integer.parseInt(tmp);
                                
                        }
                        else {
                                System.out.println("不是數字!!!");
                                return null;
                        }
                        br=null;
                        return tmp;
                }
                catch(IOException e){
                        System.out.println(e.getMessage());
                        return null;
                }
        }
        
        public static boolean isNumber(String s) {
                
                try {
             
                     Integer.parseInt(s);
                  }
                  catch(Exception e) {
     
                     return false;
                  }
                  
                  return true;
        }
}