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?
ArrayList<Robentry[]> arrList sounds like what you want.
This means arrList is a List (or ArrayList) of Robentry[].
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.
you can use Type Robentry[] to a List. like -
List<Robentry []> list = new ArrayList<Robentry []>();
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.
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.
ArrayList<RobEntry[]>, since Rb is of typeRobEntry[].Rt.add(Rb.clone());for your second problem.