import java.awt.*;
import java.awt.event.*;


class ListNode {
    String data;
    ListNode next;

    ListNode( String idata , ListNode nextNode )
    {
       data = idata;
       next = nextNode;
      
    }
}      
public class List {
	private ListNode head;
	private ListNode tail;
	private String name;
	private int size;
	
	public List( String s )
	{
		name = s;
		head = tail = null;
		size = 0;
	}
	
	public List()
	{
		this( "List" );
	}
	
    public void insertAtFront( String insertItem ) //在鏈表頭插入結點
    {
    	if ( isEmpty() )
           head = tail = new ListNode( insertItem , null );
        else
           head = new 	ListNode( insertItem ,head );
        size++;
              
     }
     
    public void insertAtBack ( String insertItem ) //在鏈表尾插入結點
    {
    	if ( isEmpty() )
           head = tail = new ListNode( insertItem , null );
        else
           tail = tail.next = new ListNode( insertItem ,null );
        size++;
           
    }
    
    public String removeFromFront() //從鏈表頭刪除并返回結點值
    {
    	String removeItem = "";
    	
           removeItem = head.data;
         
        if ( head.equals(tail) )    	
           head = tail = null;
        else
           head = head.next;
        size--;   
        return removeItem;
        
     }
     
     
     public String remove ( String item )//刪除結點值與參數相等的結點
     {
     	String removeItem = "";
     	if( head.equals(tail ) )
     	   head = tail = null;
     	else{
     		ListNode current = head;
     		while (current.data != item )
     	     	current = current.next;
     	     	removeItem = current.data;
     	     }
     	size--;    
     	     	
     	return removeItem;
     	      
     }
     
     public boolean isEmpty()//判斷鏈表是否為空
     { return head == null;}
     
     public int getSize(){ return this.size;}//取得鏈表長度
}