How can I initialize an array without knowing it size?

java arrays arraylist size variable-length-array
Space Rocker picture Space Rocker · Dec 26, 2010 · Viewed 111.8k times · Source

I have a situation, where I have to apply a criteria on an input array and reuturn another array as output which will have smaller size based upon the filtering criteria.

Now problem is I do not know the size of filtered results, so I can not initialize the array with specific value. And I do not want it to be large size will null values because I am using array.length; later on.

One way is to first loop the original input array and set a counter, and then make another loop with that counter length and initialize and fill this array[]. But is there anyway to do the job in just one loop?

Answer

Jon Skeet picture Jon Skeet · Dec 26, 2010

You can't... an array's size is always fixed in Java. Typically instead of using an array, you'd use an implementation of List<T> here - usually ArrayList<T>, but with plenty of other alternatives available.

You can create an array from the list as a final step, of course - or just change the signature of the method to return a List<T> to start with.

Related questions

Convert ArrayList<String> to String[] array

I'm working in the android environment and have tried the following code, but it doesn't seem to be working. String [] stockArr = (String[]) stock_list.toArray(); If I define as follows: String [] stockArr = {"hello", "world"}; it works. Is there something that …

Read More
Create ArrayList from array

I have an array that is initialized like: Element[] array = {new Element(1), new Element(2), new Element(3)}; I would like to convert this array into an object of the ArrayList class. ArrayList<Element> arraylist = ???;

Read More
Convert list to array in Java

How can I convert a List to an Array in Java? Check the code below: ArrayList<Tienda> tiendas; List<Tienda> tiendasList; tiendas = new ArrayList<Tienda>(); Resources res = this.getBaseContext().getResources(); XMLParser saxparser = new XMLParser(…

Read More