diff --git a/DataStructures/Stacks/StackArrayList.java b/DataStructures/Stacks/StackArrayList.java new file mode 100644 index 00000000..5093b76f --- /dev/null +++ b/DataStructures/Stacks/StackArrayList.java @@ -0,0 +1,94 @@ +import java.util.ArrayList; + +/** + * This class implements a Stack using an ArrayList. + * + * A stack is exactly what it sounds like. An element gets added to the top of + * the stack and only the element on the top may be removed. + * + * This is an ArrayList Implementation of a stack, where size is not + * a problem we can extend the stack as much as we want. + * + * @author Unknown + * + */ +public class StackArrayList{ + + /** + * Main method + * + * @param args Command line arguments + */ + public static void main(String[] args) { + StackArrayList myStackArrayList = new StackArrayList(); //Declare a stack of maximum size 4 + //Populate the stack + myStackArrayList.push(5); + myStackArrayList.push(8); + myStackArrayList.push(2); + myStackArrayList.push(9); + + System.out.println("*********************Stack List Implementation*********************"); + System.out.println(myStackArrayList.isEmpty()); //will print false + System.out.println(myStackArrayList.peek()); //will print 9 + System.out.println(myStackArrayList.pop()); //will print 9 + System.out.println(myStackArrayList.peek()); // will print 2 + System.out.println(myStackArrayList.pop()); //will print 2 + } + + /** ArrayList representation of the stack */ + private ArrayList stackList; + + /** + * Constructor + */ + public StackArrayList(){ + stackList = new ArrayList<>(); + } + + /** + * Adds value to the end of list which + * is the top for stack + * + * @param value value to be added + */ + public void push(int value){ + stackList.add(value); + } + + /** + * Pops last element of list which is indeed + * the top for Stack + * + * @return Element popped + */ + public int pop(){ + + if(!isEmpty()){ // checks for an empty Stack + + int popValue=stackList.get(stackList.size()-1); + stackList.remove(stackList.size()-1); //removes the poped element from the list + return popValue; + } + + System.out.print("The stack is already empty "); + return -1; + } + + /** + * Checks for empty Stack + * + * @return true if stack is empty + */ + public boolean isEmpty(){ + return stackList.isEmpty(); + } + + /** + * Top element of stack + * + * @return top element of stack + */ + public int peek(){ + return stackList.get(stackList.size()-1); + } +} \ No newline at end of file