How do I store an array into an element of ArrayList?

Question

Robentry [] Rb = new Robentry[robNum];

How can I store Rb into an ArrayList<E> Rt , so that Rt.get(0) == Rb is true . I do not know how to define E in the ArrayList<E> .

Edit:

If I use :

Robentry [] Rb = new Robentry[robNum];
List<Robentry []> Rt = new  ArrayList<Robentry []>();
// initialize Rb
//...
// 
Rt.add(Rb);

If I change Rb[0] , Rt.get(0)[0] is also changed. So how can I store the content of Rb into Rt so that Rt is independent of Rb ?

Answer 1

ArrayList<Robentry[]> arrList sounds like what you want.

This means arrList is a List (or ArrayList ) of Robentry[] .

Answer 2

you can use Type Robentry[] to a List. like -

List<Robentry []> list = new ArrayList<Robentry []>();

Answer 3

You can declare and use the List of type Robentry[] as below:

    //Declare a list of type Robentry[] 
    List<Robentry[]> list = new ArrayList<Robentry []>();
    //add the rb to the list
    list.add(Rb);

    //compare the list element with Rb
    System.out.println(list.get(0)==Rb);//should print true

Please note: == is fine in above example since list element is same as Rb, otherwise equals method is recommended.

Answer 4

 ArrayList<Robentry> Rt=(ArrayList<Robentry>) Arrays.asList(Rb);

or in your ways,

ArrayList<Robentry[]> Rt=new ArrayList<Robentry[]>();
rt.add(Rb);

This is called Generics,was made to ensure that the variable should contain only specific types.See this for official docs .

Answer 5

Based on your modified question, you probably want

Rt.add(Rb.clone());

or

Rt.add(Arrays.copyOf(Rb, Rb.length));

Array references are passed around by value, so you have to do an explicit copy if you want the arrays to be independent of one another.