Array initialization using reflection

Question

Someone please help to understand how can we initialize array in java using reflection.

for a simple object we can do like this :

Class l_dto_class = Class.forName(p_fld.getType().getName());
Object l_dto_obj= l_dto_class.newInstance();

but for the case of array it is giving me exception.

java.lang.InstantiationException

In order to call newInstance() you must have a zero args constructor and I don't think Array meets that requirement... — cmbaxter
– cmbaxter, Commented Jun 20, 2013 at 12:43

anubhava · Accepted Answer · 2013-06-20 12:46:34Z

16

You can instantiate array like this:

if (l_dto_class.isArray()) {
        Object aObject = Array.newInstance(l_dto_class, 5); //5 is length
        int length = Array.getLength(aObject); // will be 5
        for (int i=0; i<length; i++)
            Array.set(aObject, i, "someVal"); // set your val here
    }
}

answered Jun 20, 2013 at 12:46

anubhava

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1 Comment

Igor Zubchenok Over a year ago

To create array of l_dto_class items you need to get component class and pass it to newInstance method: Array.newInstance(l_dto_class.getComponentClass(), 5)

JEY · Accepted Answer · 2016-12-08 10:55:36Z

11

There is a class for Array in reflection java.lang.reflect.Array

int[] test = (int[])Array.newInstance(int.class, 3);

edited Dec 8, 2016 at 10:55

answered Jun 20, 2013 at 12:42

JEY

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1 Comment

johnchen902 Over a year ago

Note that you need to change test[3] to test[].

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