initialize java array vs other initialization?

Question

I know that when I initialize a char array: I have to

char[] b= new char[5];

or

char[] b= new char[5]({1,2,3,4,5});
         


        

Answer 1

If you've ever used C, then the answer is fairly simple. In C, the way you create arrays is by allocating a static length of memory on the stack that is large enough to contain the number of elements, and point to the first element with a pointer - or dynamic length of memory on the heap, and point to the first element with a pointer.

int a[5]; //stack, static allocation

int* a = (int*)malloc(sizeof(int)*5)); //heap, dynamic allocation

And in C++, the second version was changed to this, obviously because it's more obvious what is happening:

int* a = new int[5];

And they took this type of array creation over to Java.

int[] a = new int[5];

Arrays don't really work like typical objects, hence why even creating them and manipulating them with reflection uses a different Array class in order to manipulate the object. (see http://docs.oracle.com/javase/tutorial/reflect/special/arrayInstance.html )

ArrayLists are different, because they're just everyday classes like most things in java, so you initialize them with an actual constructor call:

List = new ArrayList();

Basically, arrays and classes just work in different ways.