Stack implementation in Java

StackOperations.java

public class StackOperations{
	int mystack[];
	int global_size;
	int counter = 0;
	int newcounter = 0;
	int extensionstack[]; 

	public StackOperations(int size){
		this.mystack = new int[size]; //create a stack of size as mentioned while creating object
		this.extensionstack = new int[size*100];
		this.global_size = size; //update the global variable 
	}
	//the below method will allow us to calculate the number of 
	
	public void push(int value){
		if (counter<global_size){
		mystack[counter] = value;
		counter += 1;//we have to do this unless counter < stacksize
		}
		else{
			/*so if I have to make my code work for user input greater than my initial stack size, 
			I am creating a new method called stackextender where I put new value in a new array called 
			extension stack. Then on the method, mystackmodifier I create a temparray and put contents of
			original stack and extensionstack in the temparray. At last i do mystack = temparray to 
			copy the contents to my original stack*/ 
			stackextender(value);
			counter ++;
			
		}
		
	}
	//This method puts exceeding values to a new stack called extension stack
	public void stackextender(int value){
		extensionstack[newcounter] = value;
		newcounter ++;
		}
	//This method modifies the contents of original stack 
	public void mystackmodifier(){
		int temparray[] = new int[(global_size+newcounter)*2];
		
		if(extensionstack.length>0){
			int key;
			for ( key = 0; key<mystack.length; key++){
				temparray[key] = mystack[key];
			}
		for (int i = 0; i<newcounter; i++){
			temparray[key+i] = extensionstack[i];
			}
		mystack = temparray;
		}
		
	}
	
	public int getSize(){
		return counter;
	}
	public boolean isempty(){
		if (counter==0){
			return true;
		}
		return false;
	}
	public int peek(){
		return mystack[counter-1];
	}
	
	public int pop(){
		int lastelem = mystack[counter-1];
		int afterpopped[] = new int[counter];
		counter -= 1;
		for (int i = 0; i < counter-1; i+=1){
			afterpopped [i] = mystack[i];
		}
		return lastelem;
	}	
	public String toString(){
		String output = "";
		for (int i = 0; i<counter; i++){
			output += mystack[i] + " ";
		}
		return "TOP [ "+ output + "] Bottom";
	}
}
	
//Here is the driver file
package howard.edu.ood.hw2.collections;
import java.util.*;

public class ArrayStack{
public static void main(String args[]){
	StackOperations mystack = new StackOperations(100);
	System.out.println(mystack.toString());
	/*Although the stack size is instantiated as 10, the code works for insertion for as many 
	number of items as demonstrated below*/
	for (int i = 0; i<150; i+=1){
		mystack.push(i);
	}
	
	int stacksize = mystack.getSize();
	if (stacksize == 0) {
		try{
			throw new NoSuchElementException();
		}catch (NoSuchElementException exc){
			exc.printStackTrace();
		}
	}
	System.out.println(mystack.toString());
	System.out.println("Stack size is "+ mystack.getSize());
	System.out.println("Last element is "+mystack.peek());
	System.out.println("Popping: "+ mystack.pop());	
	System.out.println("Stack size is "+ mystack.getSize());
	System.out.println("Popping: "+ mystack.pop());	
	System.out.println("Stack size is "+ mystack.getSize());

	}
}