How do I retrieve a Java Object based on a value of it's instance variables

Question

I want to add a certain Object in an ArrayList based on the user's input.

ie: If the user inputs two numbers I shall retrieve an Object of type building with given X, Y coordinates in a 2D Array I created

Answer 1

You mean something like this?

Building retrieveBuilding(Building[][] buildingMap) {
         System.out.println("Enter X");
         int x = scan.nextInt();
         System.out.println("Enter Y");
         int y = scan.nextInt();
         return buildingMap[x][y];
}

ArrayList<Building> buildings = new ArrayList<Building>();
buildings.add(retrieveBuilding(buildingMap));

I assume 2D array buildingMap is already created and contains building on all coordinates - you need to add a check for null otherwise. You should also validate input to make sure that [X,Y] is in your 2D array.

By the way, I didn't test my code and I am not sure if it does exactly what you wanted but I hope it gave you some idea.