Length of an object array

Question

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Java Arrays - length

How do you determine the length of an array that is not an String array or an integer array? It won't let me use .length(), but only .length?

Why and is there another way of determining this?

I think this will help: http://stackoverflow.com/questions/5950155/java-arrays-length — damiankolasa, Nov 26 '12 at 06:55
+ 1 fatfreddy, I was commenting with that link ;) You could determine most data type array (char, string, object, int) length using `Length` property of array object. — bonCodigo, Nov 26 '12 at 07:06

score 8 · Answer 1 · edited Apr 17 '20 at 01:56

8

You can use getLength method from java.lang.reflect.Array, which uses reflection (so it'll be slow):

Object[] anArray = new Object[2];
int length = Array.getLength(anArray);

edited Apr 17 '20 at 01:56

Dave Jarvis

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answered Nov 26 '12 at 07:01

vels4j

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score 7 · Answer 2 · answered Nov 26 '12 at 07:02

7

No matter the type an array is, we only have .length but NOT .length()

answered Nov 26 '12 at 07:02

Adrian Shum

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Isaac · Accepted Answer · 2015-03-30T07:19:35.333

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Arrays in Java are not resizable. Once an array is instantiated, its length cannot change. That's why the length attribute (myArray.length) can always be trusted to contain the array's length.

edited Mar 30 '15 at 07:19

answered Nov 26 '12 at 07:05

Isaac

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Array in Java is NOT immutable. It is just not resizable. Consider an array being a construct that holds multiple values/object-references, immutable will means once it is instantiated, we cannot change the values it is storing. However it is not the case. We can always do `myArray[2] = whatever;`. – Adrian Shum Mar 30 '15 at 04:53
@AdrianShum thank you, corrected wrong choice of words. – Isaac Mar 30 '15 at 07:19
Is the `myArray.length()` refers to how many items are in the array? – Ido Naveh Jul 21 '16 at 12:17

score 3 · Answer 4 · edited May 23 '17 at 12:09

Indeed, array length is not a method. But you still use that to determine the length of an array.

Are you saying that myArray.length() works for String or int/Integer array?

Anyway, when using array in Java, always consider if using ArrayList would suit your purpose better.

Edit: copying the useful SO link from comment of @fatfredyy to be in an answer: How is length implemented in Java Arrays?

Length of an object array

4 Answers4