Question

I have a private inner class that encapsulates some functionality. It populates two ArrayLists. I have getters for the ArrayLists that just return the private variable. Are the getters needed? Can I just make the ArrayLists public instance variables? What’s the best practice?

public class OuterClass {
    //Stuff the OuterClass does

    private class InnerClass {
        private ArrayList<String> array1;
        private ArrayList<String> array2;

        public InnerClass() {
            //Init and do stuff w/ arrays
        }

        public ArrayList<String> getArray1() {
            return array1;
        }

        public ArrayList<String> getArray2() {
            return array2;
        }
    }
}

Answer 1

Yes can make the Arraylist public, although best practice is to use getters. This allows you to build in side effects such as

• perform computation
• check constraints
• lazy initialization
• provide methods for possible inheritance

It also lets you modify the internals of your class in the future without breaking the contract.