String[] how much memory.

[adeeb alexander]

Hi all.
I want to know that if i use String[] a = new String[100], will it take any memory? If yes please tell me that how can i free it up. I also want to know that will it effect the performance if i use many times String[].

Thanks and regards
alexander

[Evan Caballero]

In my opinion, it will allocate an array object containing 100 null items.

to free it, you just have to do a = null; to dereference the array from its variable, and the garbage collector will do its job -> cleaning all unreferenced objects.

I'm not a "java memory" expert, but I think it works like this.

Why not using List<String> instead of String[] ?

[Tim McGuire]

Yes. when I did this experiment in the profiling tool JVisualVM,

public void createArrays(){


		String[] a = new String[100];

		String[] b = new String[1000];

		String[] c = new String[10000];

		String[] cc = new String[10000];

		String[] d = new String[100000];

		List<String> stringList = new ArrayList<String>();

		for(int x= 0; x< 10000; x++){

			cc[x] = "this is " + x;
			try{
				Thread.sleep(10);
			} catch (InterruptedException e){
			}
		}


	}

it looks like the Arrays take the same amount of memory whether they are populated or not.

and the List barely registered. Like Evan Caballero says, use List<String> instead if you are concerned about memory.

attached is printscreen from jvisualVM:

[adeeb alexander]

Thanks a lot for helping me out guyz.