Copying Array to another Array

Question

im trying to copy the contents of one array to another without pointing to the same memory, but i cant.

My Code:

class cPrueba {
    private float fvalor;

    public float getFvalor() {
        return fvalor;
    }

    public void setFvalor(float fvalor) {
        this.fvalor = fvalor;
    }
}

List<cPrueba> tListaPrueba = new ArrayList<cPrueba>();
List<cPrueba> tListaPrueba2 = new ArrayList<cPrueba>();

cPrueba tPrueba = new cPrueba();
tPrueba.setFvalor(50);
tListaPrueba.add(tPrueba);

tListaPrueba2.addAll(tListaPrueba);
tListaPrueba2.get(0).setFvalor(100);

System.out.println(tListaPrueba.get(0).getFvalor());

The result is "100.0" ....

Still pointing to the same object... Any short way to copy ? (without for(..){})

EDIT:

class cPrueba implements Cloneable {
    private float fvalor;

    public float getFvalor() {
        return fvalor;
    }

    public void setFvalor(float fvalor) {
        this.fvalor = fvalor;
    }

    public cPrueba clone() {
        return this.clone();
    }
}

List<cPrueba> tListaPrueba = new ArrayList<cPrueba>();
List<cPrueba> tListaPrueba2 = new ArrayList<cPrueba>();

cPrueba tPrueba = new cPrueba();
tPrueba.setFvalor(50);
tListaPrueba.add(tPrueba);

for ( cPrueba cp : tListaPrueba )
    tListaPrueba2.add(cp);

tListaPrueba2.get(0).setFvalor(100);

System.out.println(tListaPrueba.get(0).getFvalor());

Still get 100...

You'll have to clone all objects, and thus to loop over them. — Denys Séguret
– Denys Séguret, Commented Jun 1, 2013 at 15:20

fge · Accepted Answer · 2013-06-01 15:21:44Z

5

There is no way to "deepcopy" an array, or any kind of Collection (which includes List) or even Map if your object itself does not have deep copy support (for instance, via a copy constructor).

So, to your question:

Any short way to copy ? (without for(..){})

the answer is no.

Of course, if your objects are immutable, this is not a concern.

answered Jun 1, 2013 at 15:21

fge

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score 1 · Accepted Answer · 2013-06-01 15:41:36Z

1

Like dystroy said, you'll need to pass through the loop and clone all of the objects, like this:

List<cPrueba> newList = new ArrayList<cPrueba>();
for ( cPrueba cp : oldList )
    newList.add(cp.clone());

And that's assuming your object implements Cloneable, or at least has a method called clone.

So no, there is no short way (unless you write your own static method), but it is possible.

EDIT You need your clone method to return a new cPrueba:

public cPrueba clone() {
    cPrueba c = new cPrueba();
    c.setFvalor(this.getFvalor());
    return c;
}

Also, make sure you call cp.clone() in your for loop; don't just pass cp to the add method. e.g., change

tListaPrueba2.add(cp);

to

tListaPrueba2.add(cp.clone());

edited Jun 1, 2013 at 15:41

answered Jun 1, 2013 at 15:24

user1447460

Comments

Vegard · Accepted Answer · 2013-06-01 15:28:54Z

0

vanilla Java can't do this for you.

but by adding some spice you can get it done with the Dozer framework:

http://dozer.sourceforge.net/

answered Jun 1, 2013 at 15:28

Vegard

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