Question

I want to build Data main class with subclasses DataClass1(with own subclass Item) and DataClass2 (with own subclass Item1).

public class Data{

        public  List<DataClass1> dataClass1List = new ArrayList<DataClass1>();
        public  List<DataClass2> dataClass2List = new ArrayList<DataClass2>();


        public class DataClass1{

            public String name;   
            public  List<Item> itemList = new ArrayList<Item>();

            public class Item{
                public String n1;          
                public String n2;               
                public String n3;              
            }

        }


        public class DataClass2{

            public String name; 
            public  List<Item1> item1List = new ArrayList<Item1>();

            public class Item1{
                public String n5;
                public String n6;   
            }

        }

    }

When I want to fill main class Data I use this code:

Data data = new Data();
Item itm = new Item;
itm.n1="1";
itm.n2="2";
itm.n3="3";
data.dataClass1List.itemList.add(itm);

and same for dataClass2List

All sub classes must be public

Is there better way to declare and filling up my class Data

Thanks!!!

p.s. Data class and its sub classes contain only variables not methods!

Answer 1

Some suggesions:

• You should use getter and setter to access the different fields.

public class SomeClass {

    private String name;
    [...]

    public void setName(String name) {this.name = name;}
    public String getName() {return name;}
    [...]
}

• Since the Data classes are public, do they need to be inner class?

To fix this you would need to move the different public class to different files.

• All internal lists could be made `final`.

public final List<Item> itemList = new ArrayList<Item>();

• You could make a constructor for the class Item.

public class Item {
    public Item(String n1,String n2,String n3)  {
        this.n1 = n1;
        this.n2 = n2;
        this.n3 = n3;
    }
    [...]
}