linkedlist.java

package test;

public class Link {
	public static class LinkedList<E>{
		
		public class Node<E>{
			E elem;
			Node<E> next,previous;
		}
		
		public LinkedList(){};
		
		Node<E> temp = null;
		Node<E> head = null;
		Node<E> tail = null;	
		int counter = 0;
		
		public int size(){
			return counter;
		}
		
		//get element at the index
		public E getI(int index){
			
			assert(index>=0 && index<size());
			
			temp = head;
			for(int i = 0; i< index;i++){//scan tru list and find the index
				temp = temp.next;
			}
			return temp.elem;
			
		}
		
		//get index of an element
		public int getE(E elem){
			
			temp = head;
			int cnt = 0;
			//traverse through list and find element
			while(temp != null && !temp.elem.equals(elem)){
				cnt++;
				temp = temp.next;
			}
			
			if(cnt == size()){return -1;};
			return cnt;
		}
		
		//add a node at the tail
		public void add(E elem){
			//if head is null create new node
			if(head == null){
				head = new Node<E>();
				tail = head;
				head.elem = elem;
				head.next = tail;
			}
			else{
				tail.next = new Node<E>(); //tail's next becomes newnode
				tail = tail.next; // tail is new node
				tail.elem = elem;
				tail.next = null;
			}
			counter++;
		}
		
		//remove method
		public void remove(int index){//little bug, deletes 1st and 2nd element when remove(0)
			
			assert(index>=0 && index<size());
//			temp = head;
			if(index == 0){
				head = head.next;
				counter--;
				
			}
			else{
				temp = head;
				
				for(int i = 0;i<index-1; i++){
					temp = temp.next;
				}
				
				Node<E> two = new Node<E>();
				two = temp.next;
				temp.next = two.next;
				E hold = two.elem;
				two = null;
				counter--;
				//return hold;
			}
			
		}
		
		public void removeE(E elem){
			
			if(elem.equals(head.elem)){
				head = head.next;
				counter--;
			}
			
			else if(elem.equals(tail.elem)){
				tail =tail.previous;
				//tail.next = null;
				counter--;
				
			}
			else{
				Node<E> two = new Node<E>();
				temp = head;
				
				while(temp!=null && !temp.elem.equals(elem)){
					two = temp;
					temp = temp.next;
				}
				
				if(temp == null){System.out.println("elem doesn not exist");
				
				}
				else{
					two.next = temp.next;
					counter--;
				}
				
			}
			
		}
		
		public void addI(int index, E elem){
			
			if(index == size()){add(elem);}
			
			else if(index == 0){
				
				Node<E> now = new Node<E>();
				now.elem = elem;
				now.next = head;
				head.previous = now;
				head = now;
				counter++;
				
			}
			
			else{
				
				temp = head;
				for(int i = 0; i< index-1; i++){
					temp = temp.next;
				}
				
				Node<E> myNode = new Node<E>();
				myNode.elem = elem;
				myNode.next = temp.next;
				temp.next = myNode;
				counter++;
				
			}
			
		}
		
		public static void main(String[]args){
			LinkedList<Integer> linklist = new LinkedList<Integer>();
			linklist.add(1);
			linklist.add(2);
			linklist.add(3);
			linklist.addI(0,4);
			linklist.addI(1,5);
			linklist.removeE(5);
			for(int i=0;i<linklist.size();i++){
				System.out.println(linklist.getI(i));
			}
			
		}
		
	}

}