Stack implementation in Java
Stack : Stack in first in last out operated data structure ,where the first inserted (push'ed)element into the stack will be taken out (pop'ed) at last. it is like single door room . Those who enters room first will be able to come out only in the last . In other word last pushed element will be poped out first .

which we call generally as LIFO - Last In First Out

We can implement this stack using Java arrays like below ...
The below implementation takes/reads size of the stack what user want to create and implements stack operations.

Main Program :

package com.krish.stack;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class StackMain {

	public static void main(String[] args) {
		try{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String size;

		System.out.println("Enter stack size u want to create : ");
		size = br.readLine();
		System.out.println("Creating a Stack size is:"+Integer.parseInt(size));
		Stack stack = new Stack(Integer.parseInt(size));
		stack.printStackElements();
		stack.push(100);
		stack.push(200);
		stack.push(300);
		stack.pop();
		stack.pop();
		stack.pop();
		}
		catch(Exception e){
			e.printStackTrace();
		}
	}

}

Stack Class:  

package com.krish.stack;

public class Stack {
	int[] myStack;
	int top = -1;
	int size;

	public Stack(int size) {
		this.size = size;
		myStack = new int[size];
	}

	public void printStackElements() {
		if (top >= 0) {
			System.out.println("Present elements in the stack:");
			for (int i = 0; i <= top; i++) {
				System.out.println("Element at " + i + "position is "
						+ myStack[i]);
			}

		} else {
			System.out.println("Stack is empty");

		}

	}

	public void push(int element) {
		if (top < size - 1) {
			System.out.println("Pushing " + element + " to stack now");
			System.out.println("After push()");
			top++;
			myStack[top] = element;
			printStackElements();

		} else {
			System.out.println("Stack overflow; element can't be pushed");
		}
	}

	public void pop() {
		if (top >= 0) {
			System.out.println("Poping the top element now:" + myStack[top]);
			top--;
			printStackElements();
		} else {
			System.out.println("stack undeflow");
		}
	}
}

Output : 
 Enter stack size u want to create :
2
Creating a Stack size is:2
Stack is empty
Pushing 100 to stack now
After push()
Present elements in the stack:
Element at 0position is 100
Pushing 200 to stack now
After push()
Present elements in the stack:
Element at 0position is 100
Element at 1position is 200
Stack overflow; element can't be pushed
Poping the top element now:200
Present elements in the stack:
Element at 0position is 100
Poping the top element now:100
Stack is empty
stack undeflow

Advantages and disadvanaatages of using arrays in this : 
1. We can access any stack element when in array at any point of time randomly. 
2. Size is fixed we can't add more elements.
3. If we want to remove an element in between the elements then it is difficult to adjust the other elements. 
4. IF we want to insert at a particular position in between the array also it is difficult.

Reference : [1]