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Thread: Help making and iterating through ArrayList (Java Beginner)

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    Default Help making and iterating through ArrayList (Java Beginner)

    I am trying to make a list that contains four variable (integer, double, double, string). I need to create two methods. One method to add another entry to the list (but only if the integer variable is unique in the list), and another method that removes a specified entry (again, based on integer variable) from the list. I am having a lot of trouble setting up the ArrayList so that I can iterate through it in order to implement these two methods (I've tried a bunch of approaches, but nothing seems to be doing the trick). I appreciate any help with what I'm doing wrong!

    ArrayList collection=new ArrayList(); 	//initialization of trade collection
     
     
    	public void addTrade(int identifier, double amount, double rate, String currency){
    		//addTrade: inserts a single FXTrade instance into the collection
    		for (int i = 0; i < collection.size(); i++){
    			//ensure the instance is unique before adding to the list
     
    			Object currElement = collection.get(i);
    			if (currElement == collection(identifier, amount, rate, currency)){  //don't add the new trade instance if it's already in the collection
    				continue;
    			}else {
    				collection.add(identifier, amount, rate, currency);
    			}		
    		}
    	}
     
     
    	public void removeTrade(int identifier){
    		//removeTrade: removes a single FXTrade instance from the collection
     
    		//search collection for requested trade; remove the requested trade (if it's in the collection)
    		for (int i = 0; i < collection.size(); i++){
    			if (collection.get(i)==identifier){
    				collection.remove(i);
    				break;  //once the trade is removed, stop iteration (uniqueness was checked in addTrade method)
    			}
    		}
    	}


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    Default Re: Help making and iterating through ArrayList (Java Beginner)

    You need to create an Object that encapsulates those variables. It doesn't make sense to add all of them to the List at once- you need to put them into an Object, then add that Object to the List.
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    Default Re: Help making and iterating through ArrayList (Java Beginner)

    Could you give me an example of how to do that? I am trying to input and store those four pieces of information, and am stuck on how to go about doing it.

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    Default Re: Help making and iterating through ArrayList (Java Beginner)

    Recommended reading: Lesson: Classes and Objects (The Java™ Tutorials > Learning the Java Language)
    Useful links: How to Ask Questions the Smart Way | Use Code Tags | Java Tutorials
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