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package DataStructures.Stacks;

/**

* Implementation of a stack using nodes. Unlimited size, no arraylist.

*

* @author Kyler Smith, 2017

*/

public class NodeStack<Item> {

/** Entry point for the program. */

public static void main(String[] args) {

NodeStack<Integer> Stack = new NodeStack<Integer>();

Stack.push(3);

Stack.push(4);

Stack.push(5);

System.out.println("Testing :");

Stack.print(); // prints : 5 4 3

Integer x = Stack.pop(); // x = 5

Stack.push(1);

Stack.push(8);

Integer y = Stack.peek(); // y = 8

System.out.println("Testing :");

Stack.print(); // prints : 8 1 4 3

System.out.println("Testing :");

System.out.println("x : " + x);

System.out.println("y : " + y);

}

/**

* Information each node should contain.

*

* @value data : information of the value in the node

* @value head : the head of the stack

* @value next : the next value from this node

* @value previous : the last value from this node

* @value size : size of the stack

*/

private Item data;

private static NodeStack<?> head;

private NodeStack<?> next;

private NodeStack<?> previous;

private static int size = 0;

/** Constructors for the NodeStack. */

public NodeStack() {}

private NodeStack(Item item) {

this.data = item;

}

/**

* Put a value onto the stack.

*

* @param item : value to be put on the stack.

*/

public void push(Item item) {

NodeStack<Item> newNs = new NodeStack<Item>(item);

if (this.isEmpty()) {

NodeStack.setHead(new NodeStack<>(item));

newNs.setNext(null);

newNs.setPrevious(null);

} else {

newNs.setPrevious(NodeStack.head);

NodeStack.head.setNext(newNs);

NodeStack.head.setHead(newNs);

}

NodeStack.setSize(NodeStack.getSize() + 1);

}

/**

* Value to be taken off the stack.

*

* @return item : value that is returned.

*/

public Item pop() {

Item item = (Item) NodeStack.head.getData();

NodeStack.head.setHead(NodeStack.head.getPrevious());

NodeStack.head.setNext(null);

NodeStack.setSize(NodeStack.getSize() - 1);

return item;

}

/**

* Value that is next to be taken off the stack.

*

* @return item : the next value that would be popped off the stack.

*/

public Item peek() {

return (Item) NodeStack.head.getData();

}

/**

* If the stack is empty or there is a value in.

*

* @return boolean : whether or not the stack has anything in it.

*/

public boolean isEmpty() {

return NodeStack.getSize() == 0;

}

/**

* Returns the size of the stack.

*

* @return int : number of values in the stack.

*/

public int size() {

return NodeStack.getSize();

}

/**

* Print the contents of the stack in the following format.

*

* <p>x <- head (next out) y z <- tail (first in) . . .

*/

public void print() {

for (NodeStack<?> n = NodeStack.head; n != null; n = n.previous) {

System.out.println(n.getData().toString());

}

}

/** Getters and setters (private) */

private NodeStack<?> getHead() {

return NodeStack.head;

}

private static void setHead(NodeStack<?> ns) {

NodeStack.head = ns;

}

private NodeStack<?> getNext() {

return next;

}

private void setNext(NodeStack<?> next) {

this.next = next;

}

private NodeStack<?> getPrevious() {

return previous;

}

private void setPrevious(NodeStack<?> previous) {

this.previous = previous;

}

private static int getSize() {

return size;

}

private static void setSize(int size) {

NodeStack.size = size;

}

private Item getData() {

return this.data;

}

private void setData(Item item) {

this.data = item;

}

}