Re: Multidimensional arrays and arrays of arrays

From:
Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 15 Jan 2009 13:55:17 -0800
Message-ID:
<496fb154$0$12361$7836cce5@newsrazor.net>
Philipp wrote:

Hello
How can I distinguish if an array is multidimensional of if it just
contains an array? Or put it another way how can I tell at runtime
whether a/b in the example below is an array containing an array, or
if it is a multidimensional array.
If I know beforehand exactly which type it is, I can use instanceof
(see example), but I don't (especially the number of dimensions, I
don't know).
Else I can call getClass().getName() on the object and see if it
starts with "[[" (pretty ugly IMHO).
Is there another, cleaner method to do this?

public static void main(String[] args) {
  Object[] a = new Object[1];
  a[0] = new float[12];

  Object b = new float[1][12];

  if(a instanceof float[][]){
    System.out.println("a is float[][]");
  }
  if(b instanceof float[][]){
    System.out.println("b is float[][]");
  }
}

prints "b is float[][]" (but not for a) as expected.

Phil


There is no difference between a multidimensional array, and an array of
arrays. They are the same thing. Java provides a little syntactic sugar
for allocation a uniform array of arrays (of arrays etc...), but there
is no other difference, and no way to tell, other than testing each
element of every array of arrays.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>

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