How to save array changes that were made inside function?

I need to make a class for working with arrays with static generic methods. For example in this function I need to paste one array(arr2) inside other(arr1) at some index (place).

public static<T> void paste(T[] arr1, int place, T[] arr2) {
        Object[] temp = new Object[arr1.length + arr2.length];
        System.arraycopy(arr1, 0, temp, 0, place);
        System.arraycopy(arr2, 0, temp, place, arr2.length);
        System.arraycopy(arr1, place, temp, place+arr2.length, arr1.length-place);

        arr1 = (T[])temp;
    }

The function work correctly, but I cant see changes in main function. The result always remains in paste function. What can I do in this situation?

public static void main(String[] args) {
        Integer arr[] = {1 ,2 ,3 ,4, 5};
        Integer arr2[] = {11 ,22 ,33 ,44, 55};

        paste(arr, 2, arr2);
        show(arr);

    }

Solution

You can't modify the length of an existing array. Therefore, the paste method must return the new array:

public static<T> T[] paste(T[] arr1, int place, T[] arr2) {
    ...

    return temp;
}

Then, in the main method, you assigne the returned value to a new variable and use it:

T[] result = paste(arr, 2, arr2);
show(result);

Of course, you can also assign the return value to the existing variable, i.e.:

arr = paste(arr, 2, arr2);
show(arr);

Why it doesn't work the way you've tried it:

If you reassign arr1 within the paste method, it won't affect the calling method. It will only change the local variable (in fact a parameter value) within the method. The reference in the calling method (main) can't be changed from within another method.

Regarding the instantiation of the generic array:

You can instantiate an array of "correct" type (instead of an array of Objects) using reflection:

T[] temp = (T[]) Array.newInstance(arr1.getClass().getComponentType(), arr1.length + arr2.length);

Note that you still need a cast, but the runtime type of the array will be the same as the type of arr1.