Generic Stack Using Linked List And Iterator - Coursera Algorithms

To make the stack generic and to hide the internal representation of a stack from client, we can use Generics and Iterator.

Following is the program:

	package stacks;
	import java.util.Iterator;
	public class GenericStackLLIterator<Item> implements Iterable<Item> {
	private Node first = null;
	static int size = 0;
	public class Node{
	Item value;
	Node next;
	}
	@Override
	public Iterator<Item> iterator() {
	// TODO Auto-generated method stub
	return new ListIterator();
	}
	public class ListIterator implements Iterator<Item>{
	private Node current = first;
	@Override
	public boolean hasNext() {
	return (current!=null);
	}
	@Override
	public Item next() {
	Item val= current.value;
	current = current.next;
	return val;
	}
	}
	public void push(Item val) {//insert at the beginning of the LL
	Node n1 = new Node();
	n1.value = val;
	n1.next = first;
	first = n1;
	size++;
	}
	public Item pop() {//pop the first ele - LIFO
	if(isEmpty()) {
	System.out.println("stack empty");
	return null;
	}
	Item val = first.value;
	first = first.next;
	size--;
	return val;
	}
	public int size() {
	return size;
	}
	public boolean isEmpty() {
	return (first==null);
	}
	public void print() {
	System.out.println("============================================");
	Node n = first;
	while(n!=null) {
	System.out.println(n.value);
	n = n.next;
	}
	}
	public static void main(String[] args) {
	GenericStackLLIterator<Integer> stack = new GenericStackLLIterator<Integer>();
	stack.push(1);
	stack.push(2);
	stack.push(3);
	stack.push(4);
	stack.push(5);
	//stack.print();
	System.out.println("-------------Iterator-----------");
	for(Integer i: stack) {
	System.out.println(i);
	}
	stack.pop();
	stack.pop();
	stack.print();
	System.out.println("size is "+stack.size());
	stack.pop();
	stack.pop();
	stack.pop();
	stack.pop();
	//String
	GenericStackLLIterator<String> stack1 = new GenericStackLLIterator<String>();
	stack1.push("to");
	stack1.push("be");
	stack1.push("or");
	stack1.push("not");
	stack1.push("to");
	stack1.push("be");
	//stack1.print();
	System.out.println("-------------Iterator-----------");
	for(String s: stack1) {
	System.out.println(s);
	}
	stack1.pop();
	stack1.pop();
	stack1.print();
	stack1.pop();
	stack1.pop();
	stack1.pop();
	stack1.pop();
	stack1.pop();
	stack1.print();
	}
	}

view raw GenericStackLLIterator.java hosted with ❤ by GitHub