Tutorial Feedback Question - Preferred Position of Array Brackets

We received the following question this week on the tutorial feedback alias:

In some places, one comes across:

public static void main(String[] args)

while at other places it is:

public static void main(String args[])

Which is 'recommended' and why?

I know that the preferred form is String[] args, but I decided to go to the source to find out why. In this case, that would be Alex Buckley, lead of the JLS (Java Language Specification) and JVMS (Java Virtual Machine Specification). In Alex's own words:

String[] is preferred because it keeps the type of args — array of String — all together. In a more complicated and poorly formatted method signature, it could be easy to miss a [] after a parameter name.

Which is pretty much what I thought. Alex goes on to point out that the following statements are equivalent:

String[][] s;
String[]   s[];
String     s[][];

However, the middle form is a maintenance headache and is not recommended. In general, arrays cause all sorts of problems at runtime — bounds must be checked as well as the runtime type of the array:

Object[] o = new String[5];
o[0] = new Integer(1);  //Compiles OK, but gives ArrayStoreException

For these reasons and because they offer more flexible options, the Collections classes are preferred to arrays. You might want to check out our Collections tutorial, written by Josh Bloch, author of the well known book, Effective Java.

Thanks, Alex!

-- Sharon Zakhour

Posted at 04:55PM Oct 23, 2007 by The Java Tutorial Team  |  Comments[7]