Data Structures and Algorithm Analysis

Lesson 3: Stack Implementation without Array

Java Collection framework provides a Stack class which models and implements Stack data structure. The class is based on the basic principle of last-in-first-out. In addition to the basic push and pop operations, the class provides three more functions of empty, search and peek. The class can also be said to extend Vector and treats the class as a stack with the five mentioned functions. The class can also be referred to as the subclass of Vector. This diagram shows the hierarchy of Stack class:

The class supports one default constructor Stack() which is used to create an empty stack.

Methods in Stack class

1. Object push(Object element) : Pushes an element on the top of the stack.
2. Object pop() : Removes and returns the top element of the stack. An EmptyStackException exception is thrown if we call pop() when the invoking stack is empty.
3. Object peek() : Returns the element on the top of the stack, but does not remove it.
4. boolean empty() : It returns true if nothing is on the top of the stack. Else, returns false.
5. int search(Object element) : It determines whether an object exists in the stack. If the element is found, it returns the position of the element from the top of the stack. Else, it returns -1.

Source Code:

Output:

Iterable EXTENDS Collection INTERFACE EXTENDS List IMPLEMENTS Vector EXTENDS Class Stack