If the individual elements of an int array are not initialized, what is stored in them by default? I apparently found that there is something like an empty array or a null array. What is the difference, and which one applies to my first question?
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1You can have a zero-length array -- contains no elements. You can have a null array reference -- the reference is null, meaning that no array actually exists. You can have an array with elements that are all set to null -- this is the default for an array of references when it's initially created.Hot Licks– Hot Licks2014-12-15 03:17:55 +00:00Commented Dec 15, 2014 at 3:17
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4 Answers
Technically speaking, there's no such thing as a null array; but since arrays are objects, array types are reference types (that is: array variables just hold references to arrays), and this means that an array variable can be null rather than actually pointing to an array:
int[] notAnArray = null;
An empty array is an array of length zero; it has no elements:
int[] emptyArray = new int[0];
(and can never have elements, because an array's length never changes after it's created).
When you create a non-empty array without specifying values for its elements, they default to zero-like values — 0 for an integer array, null for an array of an object type, etc.; so, this:
int[] arrayOfThreeZeroes = new int[3];
is the same as this:
int[] arrayOfThreeZeroes = { 0, 0, 0 };
(though these values can be re-assigned afterward; the array's length cannot change, but its elements can change).
1 Comment
Sriman S
And default value is false for a boolean array
An array has its members initialized to their default values. For int the default is 0. For an Object it's null. A null array is a null Array Reference (since arrays are reference types in Java).
JLS-4.12.5 Initial Values of Variables says in part
For type int, the default value is zero, that is, 0.
and
For all reference types (§4.3), the default value is null.
3 Comments
Elliott Frisch
@Quantitative Correct. And for an
Integer[], but a double[] would default to 0 (being a primitive type).
Thomas Weller
The index 0 in
int[] a = new int[0] has nothing to do with default valuesElliott Frisch
@ThomasWeller
int[] a = new int[1]; has a default value at index 0. In fact, any array length greater than 0 has a default value at index 0.By default java initialized the array according to type declared. It is int then it is initialized to 0. If it is of type object like array of object then it is initialized to null.
Comments
If the individual elements of an int array are not initialized, what is stored in them by default?
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empty array is array with 0 elements
I haven't heard about null array but it is probably an array with non zero element reference which are null
