[webhound2]

I'm trying to search this ArrayList but it comes back false every time. Below are the two methods that interact with one another. And below that is the TallyItem class that comprises the ArrayList.

public int getItemCount(String item)
	{


		if(!items.isEmpty())
		{
			this.item=item;

			if(searchArray(item))
			{
				count=tempItem.getCount();
				return count;
			}

			else
			{
				JOptionPane.showMessageDialog(null, "The item, " + item +", doesn't exist.", "Item Not Found", JOptionPane.ERROR_MESSAGE);
				return 0;
			}
		}
		else
		{
			JOptionPane.showMessageDialog(null, "There are no items in the tally.", "Item Not Found.", JOptionPane.ERROR_MESSAGE);
			return 0;
		}

	}



public boolean searchArray(String item)
	{
		counter=0;
		while(!found && counter<items.size())
		{
			tempItem = items.get(counter);
			if(tempItem.getName()==item)
			{
				found = true;
				return found;
			}
			else
				counter++;

		}
		return found;
	}



public class TallyItem
{
	private static String name;
	private static int count;

	public TallyItem(String name, int count)
	{
		this.name=name;
		this.count=count;
	}

	public static String getName()
	{
		return name;
	}

	public static int getCount()
	{
		return count;
	}

	public static void setCount(int addCount)
	{
		count+=addCount;
	}

}

[bcranger]

Strings are compared for equality with the equals() method, the "==" operator will only test to see if it is the same object w/ same reference.

I think you are overcomplicating your search. If you want to search to see if an item is in your arraylist, just iteratre through until you stumble across it.

public int searchArray(String name)
{
  for(int i = 0; i < yourArray.size(); i++)
  {
    if(yourArray.get(i).getName().equals(name))
      return i;
  }
  return -1;
}

[webhound2]

Thanks, for that bcranger. I'm still learning this stuff and that's real helpful. I always wonder about concatenating*? method call. This helps alot. I could've sworn I'd compared strings to empty strings using "" and == before, but this seems like a better way to do it.

[macosxnerd101]

Behind the scenes, there is a String pool to help with memory efficiency. As an example, rather than have 1000 "" String objects in memory, only 1 "" is stored in memory, and it is continually referenced. So b/c the memory addresses are the same, the == operator works. However, you are guaranteed an accurate check with equals() vs. ==. The same applies to all Strings with the String pool, just using "" as an example.

[webhound2]

macosxnerd101, on 22 August 2010 - 11:00 AM, said:

Behind the scenes, there is a String pool to help with memory efficiency. As an example, rather than have 1000 "" String objects in memory, only 1 "" is stored in memory, and it is continually referenced. So b/c the memory addresses are the same, the == operator works. However, you are guaranteed an accurate check with equals() vs. ==. The same applies to all Strings with the String pool, just using "" as an example.

I'm pretty new at this. What is a String pool? Does it have anything to do with args in the main method?

[macosxnerd101]

The String pool allows for storing unique Strings rather than a String each time one is assigned. So:

String x = "";
String y = "";

There is only one "" in memory b/c of the String pool. There are plenty of links if you want to read more about it, but the String pool makes it safer in certain instances to compare Strings using ==, but to be 100% sure, compare using equals().

[Dogstopper]

macosxnerd101, on 22 August 2010 - 04:11 PM, said:

The String pool allows for storing unique Strings rather than a String each time one is assigned. So:

String x = "";
String y = "";

There is only one "" in memory b/c of the String pool. There are plenty of links if you want to read more about it, but the String pool makes it safer in certain instances to compare Strings using ==, but to be 100% sure, compare using equals().

That's pretty advanced for him I think. However, if you think about every object that you make as simply a gateway to the memory, then this makes sense. In mac's example, those aren't two separate objects, they are two different gateways (references) to the SAME piece of memory because the values of the Strings are the same. Make sense?

[macosxnerd101]

Maybe a little advanced and not really necessary to know at this point if he uses equals() exclusively, but just providing more explanation in regards to his question about why == works sometimes with Strings.

[webhound2]

macosxnerd101, on 22 August 2010 - 05:53 PM, said:

Maybe a little advanced and not really necessary to know at this point if he uses equals() exclusively, but just providing more explanation in regards to his question about why == works sometimes with Strings.

It makes sense, I think. When using == you're looking for a memory location instead of the item within the quotes...I think. So you end up asking whether or not the item is in the same location instead of asking for exact equality. That's what I make of it, anyway.

[Dogstopper]

webhound2, on 22 August 2010 - 09:52 PM, said:

It makes sense, I think. When using == you're looking for a memory location instead of the item within the quotes...I think. So you end up asking whether or not the item is in the same location instead of asking for exact equality. That's what I make of it, anyway.

Yep. You got it. Most of the time, that's a bad thing to do with objects( == ), but with certain Strings, its ok to do.

[m-e-g-a-z]

@webhound2, If you want to check whether a specific element is in the ArrayList, you can use the contains() method thats returns true/false depending on if the element in the params being tested is in the ArrayList or not.

[pbl]

m-e-g-a-z, on 23 August 2010 - 02:58 PM, said:

@webhound2, If you want to check whether a specific element is in the ArrayList, you can use the contains() method thats returns true/false depending on if the element in the params being tested is in the ArrayList or not.

Actually never checked that one
Returns true/false depending on if the element in the params being tested is in the ArrayList or not
or
Returns true if the element in the params being tested equals method return true when compared with one of the element in the arraylist

???

[bcranger]

pbl, on 23 August 2010 - 03:40 PM, said:

m-e-g-a-z, on 23 August 2010 - 02:58 PM, said:

@webhound2, If you want to check whether a specific element is in the ArrayList, you can use the contains() method thats returns true/false depending on if the element in the params being tested is in the ArrayList or not.

Actually never checked that one
Returns true/false depending on if the element in the params being tested is in the ArrayList or not
or
Returns true if the element in the params being tested equals method return true when compared with one of the element in the arraylist

???

Oops...pressed +1 instead of reply lol

But the answer to your question is the former. Just checks to see if param is contained within array.

[m-e-g-a-z]

bcranger, on 23 August 2010 - 10:47 PM, said:

Oops...pressed +1 instead of reply lol

But the answer to your question is the former. Just checks to see if param is contained within array arraylist.

Make things clearer

This post has been edited by m-e-g-a-z: 23 August 2010 - 05:03 PM

[pbl]

You are wrong bot of you
Here is the proof:

public class Contains {
	public static void main(String[] args) {
		String a, c;
		
		// just to make sure the 2 String do not point to the same object
		a = new String("abc");
		c = new String("abc");
		System.out.println("Is a == c: " + (a == c) + " just to be sure");
		
		ArrayList<String> al = new ArrayList<String>();
		al.add(a);
		// test if contained
		System.out.println("Does the ArrayList contains c: " + al.contains(c));
	}
}

prints out

Is a == c: false just to be sure
Does the ArrayList contains b: true

So the contains() method check if the searched object equals method returns equality with an object contained in the ArrayList not if the searched object is effectively in the ArrayList

So the code of contains should look like

boolean contains(Object o) {
   for(int i = 0; i < size; i++) {
     if(array[i].equals(o))
       return true;
   }
   return false;
}

and not

boolean contains(Object o) {
   for(int i = 0; i < size; i++) {
     if(array[i] == o)
       return true;
   }
   return false;
}

as you seem to think (to though I hope)

After all bcranger my +1 was desserved

This post has been edited by pbl: 23 August 2010 - 06:47 PM
Reason for edit:: Dammed b) changed to c