Added NodeStack.java, another stack implementation

data_structures/Stacks/NodeStack.java

@@ -0,0 +1,183 @@
+/**
+* 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 = 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 = 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.
+    *
+    * 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;
+	}
+}