Question

I need to create an Arraylist in a while loop with a name based on variables also in the loop. Here’s what I have:

while(myScanner.hasNextInt()){    

    int truster = myScanner.nextInt();
    int trustee = myScanner.nextInt();
    int i = 1;
    String j = Integer.toString(i);
    String listname = truster + j;

    if(listname.isEmpty()) {
        ArrayList listname = new ArrayList();
    } else {}
    listname.add(truster);

    i++;
}

The variable truster will show up more than once while being scanned, so the if statement is attempting to check if the arraylist already exists. I think I might have done that out of order, though.

Thanks for your help!

Answer 1

Store the ArrayLists in a Map:

Map<String, List<String> listMap = new HashMap<String,List<String>>();
while (myScanner.hasNextInt()){    
    // Stuff
    List<String> list = new ArrayList<String>();
    list.add(truster);
    listMap.put(listname, list);
}

Note the use of generics (the bits in <>) to define the type of Object the List and Map can contain.

You can access the values stored in the Map using listMap.get(listname);