This implementation of a stack has been built using Java and generics, so it can be used with custom objects. It is based upon a Node class, which contains the data that has to be stored (data) and a reference to the node below it in the stack (nextNode). The stack itself consists of a reference to the top node (top) and an integer that indicates the total height of the stack (numElem).

The methods implemented are the following:

• Constructor: creates an empty stack.
• push(): adds a new element to the stack. The element must be indicated as an argument.
• pop(): removes and returns the element on the top of the stack.
• empty(): returns a boolean indicating if the stack is empty or not.
• size(): returns an integer indicating the size of the stack.
• peek(): returns the element on the top of the stack without removing it.

The exceptions used are:\

• StackIsEmpty: in case the pop() or peek() methods cannot get the element on the top because the stack is empty.