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

  1. #1
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    Default 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)
    Last edited by gamerlovo; April 2nd, 2014 at 12:37 PM.


  2. #2
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    Default Re: If you can, show me what i am doing wrong

    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.
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