Java program that implements stack ADT

import java.util.Scanner;
class stack<E>
{
private final int size;
private int top;
private E[] elements;
public stack()
{
this(10);
}
public stack(int s)
{
size=s>0?s:10;
top=-1;
elements=(E[])new Object[size];
}
public void push(E x)
{
if(top==size-1)
System.out.println("Overflow");
elements[++top]=x;
}
public E pop()
{
if(top==-1)
System.out.println("Underflow");
return elements[top--]; 
}
public void display()
{
if(top==-1)
System.out.println("Stack is empty");
else
{
for(int i=0;i<top;i++)
System.out.println(elements[i]);
}
}
}
 
public class stacktest
{
public static void main(String[] args)
{
int ch,ch1;
stack<Double>d_stack;
d_stack=new stack<Double>(5);
Scanner input=new Scanner(System.in);
do
{
System.out.println("Menu is as follows:");
System.out.println("1.Push\n2.Pop\n3.Display\n4.Exit");
System.out.println("Enter your choice:");
ch=input.nextInt();
switch(ch)
{
case 1:	System.out.println("Enter element to push:");
double item=input.nextInt();
d_stack.push(item);
break;
case 2:	double item1=d_stack.pop();
System.out.println("Popped item:"+item1);
break;
case 3:	d_stack.display();
break;
default:	break;
}
}while(ch!=4);		
}
}