java - Why I am not able to Pop Element from stack using Linked List Implementation? -

problem:

i not able pop element second time. example have 4,3,2,1 4 on top of stack.i not able delete 3,2

can guide me why?

below stack implementation :

public static void push(int data){         if(head==null){             node newnode=new node(data);             head=newnode;         }else{             node newnode1=new node(data);             newnode1.next=head;             head=newnode1;     }      }     public static int pop(){         if(head==null){             return 0;         }         else{             node temp=head;             int a=temp.data;             temp=null;             return a;         }     }     public static void traverse(){         node temp=head;         while(temp!=null){             system.out.println(temp.data);             temp=temp.next;          }     } 

you have problem in pop method

  public static int pop(){     if(head==null){         return 0;     }     else{         node temp=head;         head = head.next;         int a=temp.data;         temp=null;         return a;     } } 

you forgot move head next node.