From b58bf59f2c2f3e40f381b4ce69a7d4f3a95235cb Mon Sep 17 00:00:00 2001
From: Yash Bhansali <bhansaliyashg@gmail.com>
Date: Fri, 10 Mar 2017 00:35:22 +0530
Subject: [PATCH] Stack ArrayList Implementation

---
 data_structures/Stacks.java | 62 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

diff --git a/data_structures/Stacks.java b/data_structures/Stacks.java
index 7fdf6133fb45..6465533d29d5 100644
--- a/data_structures/Stacks.java
+++ b/data_structures/Stacks.java
@@ -38,6 +38,50 @@ public void makeEmpty(){ //Doesn't delete elements in the array but if you call
 		top = -1;			 //push method after calling makeEmpty it will overwrite previous values
 	}
 }
+
+
+/* This is ArrayList Implementation of stack , Where size is not a problem we can extend the stack as much as we want*/ 
+class Stack2{
+		
+		
+		ArrayList<Integer> stackList;
+		
+		Stack2(){ //constructor
+			stackList=new ArrayList<>();
+		}
+		
+		
+		void push(int value){ //adds value to the end of list which is the top for stack
+			stackList.add(value);
+		}
+		
+		int pop(){ //pops last element of list which is indeed the top for Stack 
+			
+			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;
+			}
+			else{
+				System.out.print("The stack is already empty  ");
+				return -1;
+			}
+			
+		}
+		
+		boolean isEmpty(){ //checks for empty Stack
+			if(stackList.isEmpty())
+				return true;
+			
+			else return false;
+			
+		}
+		
+		int peek(){ //top element of stack
+			return stackList.get(stackList.size()-1);
+		}
+	}
 //Example
 public class Stacks{
 	public static void main(String args[]){
@@ -48,10 +92,26 @@ public static void main(String args[]){
 		myStack.push(2);
 		myStack.push(9);
 
+		System.out.println("*********************Stack Array Implementation*********************");
 		System.out.println(myStack.isEmpty()); //will print false
 		System.out.println(myStack.isFull()); //will print true
 		System.out.println(myStack.peek()); //will print 9
 		System.out.println(myStack.pop()); //will print 9
 		System.out.println(myStack.peek()); // will print 2
+		
+		Stack2 myStack2 = new Stack2(); //Declare a stack of maximum size 4
+		//Populate the stack
+		myStack.push(5);
+		myStack.push(8);
+		myStack.push(2);
+		myStack.push(9);
+
+		System.out.println("*********************Stack List Implementation*********************");
+		System.out.println(myStack.isEmpty()); //will print false
+		System.out.println(myStack.peek()); //will print 9
+		System.out.println(myStack.pop()); //will print 9
+		System.out.println(myStack.peek()); // will print 2
+		System.out.println(myStack.pop()); //will print 2
+		
 	}
-}
\ No newline at end of file
+}