Bag of Objects : Remove method

Hello! I am creating a program that creates a Bag of different Objects. These can be integers, Strings, doubles, etc. I have created a bag and put in int's and a few Strings. I can display the bag with no errors. However now I am running into a problem. I have this remove method that is supposed to iterate through my array that contains the Objects and remove any Object that collect[i].equals. I am getting a null pointer error. Any suggestions?

Remove method:

public void remove(Object item){
		if (this.size() > 0){
			for (int i = 0; i < collect.length; i++){
				if (collect[i].equals(item)){
					collect[i] = null;
					count_ItemsRandomlyRemoved++;
					counter--;
				}
			}
		}else{
			System.out.println("The item was not found in the bag");
		}
	}

Calling it in main method (2, and "CSCI" are both in the bag):

bag1.remove(2);
		bag1.remove("CSCI");