Java Object reference

Question

This is regarding the usage of ArrayList returned by another class instance variable.

Class A {

    //assigned list of string to it.
    private List < String > newAl;
    //returns the list
    public List < String > getList() {
        return newA1;
    }
}

Class Test {

    public void go() {
        List < String > list = a.getList();
        list.add("");
    }

}

In the Test class when i retreive list and manipulate the list.Because of the reference ,class A list also got manipulated.If A is part of third party code.How do I correct my code in Test class so that original object wouldnt be affected?

return a copy of newAl?

asgs
– asgs

2013-05-21 05:08:01 +00:00
Commented May 21, 2013 at 5:08 — asgs
– asgs, Commented May 21, 2013 at 5:08
You need to clone the list before sending.

Subir Kumar Sao
– Subir Kumar Sao

2013-05-21 05:08:29 +00:00
Commented May 21, 2013 at 5:08 — Subir Kumar Sao
– Subir Kumar Sao, Commented May 21, 2013 at 5:08
Or after sending, depending on what A actually is.

gsgx
– gsgx

2013-05-21 05:08:57 +00:00
Commented May 21, 2013 at 5:08 — gsgx
– gsgx, Commented May 21, 2013 at 5:08
Thanks for replying .I can manipulate only Test class.

devv
– devv

2013-05-21 05:16:54 +00:00
Commented May 21, 2013 at 5:16 — devv
– devv, Commented May 21, 2013 at 5:16

gsgx · Accepted Answer · 2013-05-21 05:10:34Z

2

The ArrayList constructor takes a Collection so you can use that:

List<String> list = new ArrayList(a.getList());

I think it's better to do it like this, but depending on what you're doing, you may want to construct the new List in the getter. That also helps type hiding.

answered May 21, 2013 at 5:10

gsgx

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