Thread: Why use "new" operator with an instance variable of array type in accessor methods?

if you please explain more about array of objects and why we Do use new operator in accessor methods?
accessor methods are only for returning values, but on this example they create object at line 25 ,instead of returning elements of array a, directly?

 
public class ToyExample
6 {
7 private Date[] a;
8 public ToyExample(int arraySize)
9 {
10 a = new Date[arraySize];
11 for (int i = 0; i < arraySize; i++)
12 a[i] = new Date();
13 }
14 public ToyExample(ToyExample object)
15 {
16 int lengthOfArrays = object.a.length;
17 this.a = new Date[lengthOfArrays];
18 for (int i = 0; i < lengthOfArrays; i++)
19 this.a[i] = new Date(object.a[i]);
20 }
21 public Date[] getDateArray()
22 {
23 Date[] temp = new Date[a.length];
24 for (int i = 0; i < a.length; i++)
25 temp[i] = new Date(a[i]);
26 return temp;
27 }

I'm sorry the title is long.

thanks
but I'm asking why don't we displaying a element directly?
I mean without create temp array?

how i can read the API to read about?
i use eclipse.

on this example they create object at line 25 ,instead of returning elements of array a, directly

In fact it is on line 23 that they create the new object they will return (temp). The for loop is used to populate this new array with new Date objects.

The reason is so that the caller does not get a reference to the private Date array a. If they did they could change the contents of the array - so that it would be all that private. It is common for accessors to return not some piece of private state, but a copy that the caller cannot modify.

Originally Posted by pbrockway2

In fact it is on line 23 that they create the new object they will return (temp). The for loop is used to populate this new array with new Date objects.

The reason is so that the caller does not get a reference to the private Date array a. If they did they could change the contents of the array - so that it would be all that private. It is common for accessors to return not some piece of private state, but a copy that the caller cannot modify.

thank you
i am appreciated for your help.

Could you please write the statement of the caller?

ToyExample eg = new ToyExample(666);
Date[] arr = eg.getDateArray();
 
arr[42] = new Date(); // this will *not* change the array entry in the ToyExample instance

thanks a lot.

--- Update ---

i want to display array a elements
how to write method toString() for it?

Either use the Arrays.toString() method, or use a for loop to build up or display your string.

Originally Posted by pbrockway2

Either use the Arrays.toString() method, or use a for loop to build up or display your string.

i've used for loop in toString() method.