There is a few things you can do with arrays which are surprising.
Is it an array or not?
Serializable array = new Serializable[9];
Is array an array or a scalar? Well its a scalar which points to an array. Just like
Object o = new Object[9];
You can assign an array to an object because it is also an object. However, arrays are also Serializable so you can assign them to Serializable.
Where did my [] go?
The [] can appear in surprising places. This compiles for backward comparability reasons.
public static int method(int[]... args)[] {
return args[0];
}
And the types here are; args is an int[][] and the return type is int[]. Did you notice the [] after the method declaration! This is not part of the JLS and the OpenJDK allows this due to backward compatibility reasons.
What is the difference between int[] array and int array[] ?
There is a difference in what comes after it.
int[] array, x[];
and
int array[], y[];
In these cases; x is an int[][] but y is only an int[].
What happens if an array initialization is too large?
Say I initialize an array like this
public static final int[] VALUES = {
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,
/* many, many lines deleted */
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,
};The errors message is;
Error:(6, 31) java: code too large
This seems a little strange. It doesn’t complain the array is too large. In fact if I have more static fields or use larger constants, it will fail for a smaller array.
This happens because arrays are initialised in byte code. There byte code creates the array and initialises each value, one at a time. This results in a lot of code for large arrays which would be such a problem if there wasn’t a limit in the size of a method. i.e. 65535 bytes. The compiler generates one and only one method for a constructor or static initialization so this limits how many enums you can have and how large your initialised arrays can be.
| Reference: | Java arrays, Wat!? from our JCG partner Peter Lawrey at the Vanilla Java blog. |
