Thread: If you can, show me what i am doing wrong

i am working on a assignment that has to do with array lists, it mainly has to do with adding new elements, telling then where it is it located, if the memory block is empty , ect. so far i have been having problems with my indexOf method which should display the array cell number that a input element E is in, and if it is not in there it should display a -1.

public class MyArrayList<E> 
{
	private E[] data_store = (E[])new Object[2];
	private int sizeofa = 0;
 
	private void resize()// makes the array list bigger if need
	{
		E[] bigspacemaker = (E[])new Object[data_store.length * 2];
		for(int x = 0 ; x< sizeofa ; x++)
		{
			bigspacemaker[x]= data_store[x];
		}
		data_store = bigspacemaker ;
	}
 
	public int indexOf(E element) // should returns the index of the given element. Returns -1 if element was not found.
	{
		boolean pass = false;
		 ;
		int o = 0 ;
 
		while (element!= data_store[o])
		{
			o++;
			if (element.equals(data_store[o]))//Eclipse says that the problem is here
			{
				pass = true;
			}
 
		}
 
 
		if (pass == false)
		{
			int z = -1;
			return z;
		}
 
		else
		{
			return o;
		}
 
	}
 
 
 
	public void add(E element)// adds elements
	{
		if (sizeofa == data_store.length)
		{
			resize();
		}
		data_store[sizeofa] = element;
		sizeofa++;
	}
 
	public boolean contains(E element)//checks to see if the array list contains a spesific element 
	{
		boolean a = false;
		int count = 0 ;
		while (count < sizeofa )
		{
			if ( data_store[count]  == element  )
			{
				a = true;
 
			}
			count++;
		}
		return a;
	}
 
	public boolean isEmpty()// checks if array cell is empty
	{
		if (data_store[0]==null)
		{
			return true;
		}
		else
		{
			return false;
		}			
	}
 
	public E get(int index) 
	{
		return data_store[index];
	}
 
	public int size() 
	{
		return sizeofa;
	}
 
 
 
}

and here is the code that tests it out

public class MyArrayListDemo1 {
	public static void main(String[] args)
	{
		MyArrayList<String> t = new MyArrayList<String>();
		System.out.println("isEmpty? " + t.isEmpty());
		t.add("Santa Maria");
		t.add("Los Angeles");
		t.add("Ventura");
		t.add("Thousand Oaks");
		System.out.println("isEmpty? " + t.isEmpty());
		System.out.println("Contains Santa Maria? " + t.contains("Santa Maria"));
		System.out.println("Contains Los Angeles? " + t.contains("Los Angeles"));
		System.out.println("Contains Junk data 75? " + t.contains("Junk data 75"));
		System.out.println("Contains Ventura? " + t.contains("Ventura"));
		System.out.println("Contains Thousand Oaks? " + t.contains("Thousand Oaks"));
		System.out.println("Contains Simi Valley? " + t.contains("Simi Valley"));
		System.out.println("Contains Westlake? " + t.contains("Westlake"));
 
		for (int x = 0; x < 500; x++)
		{
			t.add("Junk data " + x);
		}
		System.out.println("isEmpty? " + t.isEmpty());
		System.out.println("indexOf Ventura: " + t.indexOf("Ventura"));
		System.out.println("indexOf Junk data 75: " + t.indexOf("Junk data 75"));// it crashes right here
		System.out.println("indexOf Santa Maria: " + t.indexOf("Santa Maria"));
		System.out.println("indexOf Thousand Oaks: " + t.indexOf("Thousand Oaks"));
		System.out.println("indexOf Junk data 499: " + t.indexOf("Junk data 499"));
		System.out.println("indexOf Los Angeles: " + t.indexOf("Los Angeles"));		
		System.out.println("indexOf Junk data 123: " + t.indexOf("Junk data 123"));
 
		System.out.println("isEmpty? " + t.isEmpty());
		System.out.println("--------");
		System.out.println("Cool!  I didn't crash!");
	}
}

please help me i am really confused on why it dosen't work
sorry but i forgot to put in the error message:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 512
at MyArrayList.indexOf(MyArrayList.java:28)
at MyArrayListDemo1.main(MyArrayListDemo1.java:26)

Please post the errors you get when you run the codes. Btw, your use of o for 0 wouldn't work as a position holder in an array.