Thread: Re-Initialize array without loosing contents..

Hello everyone!!!
Suppose, i've declared a string array. At runtime, i get user's choice and initialize the array size with user given choice.

Now, suppose

String array[];

During run-time user entered 5 and my array size is now 5. Now if a specific condition occur, i want to resize my array. Forexample, a condition occured, and i needed to add 5 more indexes in the array. Means, my array should be of size 10 now without any data loss. I know how to handle the data without loosing it but don't know how to re-initialize my same array to get size 10. I only want to use array and nothing else (i.e. arraylist or vector).

And is this the right solution (Described below);
i'll make a function which will initialize my array with user given size. As soon as user enters, array is declared and soon after as i need to extend my array size, i'll call the function. Before that, i'll store whole data in temporary array.

So, if there are other solutions (efficient one), kindly let me know.

Waiting....

Regards...

Originally Posted by Mr.777

i needed to add 5 more indexes in the array. ... how to re-initialize my same array to get size 10.

And is this the right solution (Described below);
i'll make a function which will initialize my array with user given size. As soon as user enters, array is declared and soon after as i need to extend my array size, i'll call the function. Before that, i'll store whole data in temporary array.

well depends on if you know how many elements they are going to enter.
run this code and you can decide what you want to create.

    public static void main(String[] args) {
        System.out.println("staring a Array[] with 5 elements");
        String[] myString ={"Bob","Tim","Robert","Julie","Mark"};
        System.out.println("my array has this many elements: " + myString.length);
        System.out.println("assign a new array with 10 elements");
 
        /*created a new String array*/
        String[] newString = new String[myString.length * 2];
 
        /*loop to assign my new elements */
        for (int i = 0; i < myString.length; i++) {
            newString[i]=myString[i];
            System.out.println("string name is " + myString[i]);
        }
 
        System.out.println("this is how many elements my new string has: " + newString.length);
        /*reference assignment*/
        myString = newString;
        System.out.println("myString has this many elements: " + myString.length);
    }
}

call a functions similar to this when you know that you have to double your elements in your array[] then you wont have to worry about it.
call it expandingArray() method.

Thanks to both of you for helping me.
But, unfortunatley i couldn't get any new thing.
@helloworld922: What you are saying, will be efficient in other cases, but in my case, it's really not as i just need to save as much memory as i can.
@william : The same thing i was thinking and wrote above.

Anyways, thanks alot, both of you.

May you stay happy always.

Good luck.

You can use the Arrays.copyOf(..) methods to copy the contents of an existing array into a longer one. Basically they use System.arraycopy(..) to copy the array contents. In the end, it's just a slightly better way to do what the other code posted here does.

@dlorde: Thanks alot. I'll definitely give it a try and if problem persists, i'll come back here

@helloworld922: Sure and thanks again. I'll study about radix trees in depth. Thanks for support.