Difference between int[] array and int array[]

Question

I have recently been thinking about the difference between the two ways of defining an array:

1. int[] array
2. int array[]

Is there a difference?

Answer 1

They are semantically identical. The int array[] syntax was only added to help C programmers get used to java.

int[] array is much preferable, and less confusing.

Answer 2

There is one slight difference, if you happen to declare more than one variable in the same declaration:

int[] a, b;  // Both a and b are arrays of type int
int c[], d;  // WARNING: c is an array, but d is just a regular int

Note that this is bad coding style, although the compiler will almost certainly catch your error the moment you try to use d.

Answer 3

There is no difference.

I prefer the type[] name format at is is clear that the variable is an array (less looking around to find out what it is).

EDIT:

Oh wait there is a difference (I forgot because I never declare more than one variable at a time):

int[] foo, bar; // both are arrays
int foo[], bar; // foo is an array, bar is an int.

Answer 4

No, these are the same. However

byte[] rowvector, colvector, matrix[];

is equivalent to:

byte rowvector[], colvector[], matrix[][];

Taken from Java Specification. That means that

int a[],b;
int[] a,b;

are different. I would not recommend either of these multiple declarations. Easiest to read would (probably) be:

int[] a;
int[] b;

Answer 5

From section 10.2 of the Java Language Specification:

The [] may appear as part of the type at the beginning of the declaration, or as part of the declarator for a particular variable, or both, as in this example:

 byte[] rowvector, colvector, matrix[];

This declaration is equivalent to:

byte rowvector[], colvector[], matrix[][];

Personally almost all the Java code I've ever seen uses the first form, which makes more sense by keeping all the type information about the variable in one place. I wish the second form were disallowed, to be honest... but such is life...

Fortunately I don't think I've ever seen this (valid) code:

String[] rectangular[] = new String[10][10];

Answer 6

The two commands are the same thing.

You can use the syntax to declare multiple objects:

int[] arrayOne, arrayTwo; //both arrays

int arrayOne[], intOne; //one array one int 

see: http://java.sun.com/docs/books/jls/second_edition/html/arrays.doc.html

Answer 7

No difference.

Quoting from Sun:

The [] may appear as part of the type at the beginning of the declaration, or as part of the declarator for a particular variable, or both, as in this example: byte[] rowvector, colvector, matrix[];

This declaration is equivalent to: byte rowvector[], colvector[], matrix[][];

Answer 8

There isn't any difference between the two; both declare an array of ints. However, the former is preferred since it keeps the type information all in one place. The latter is only really supported for the benefit of C/C++ programmers moving to Java.

Answer 9

There is no real difference; however,

double[] items = new double[10];

is preferred as it clearly indicates that the type is an array.

Answer 10

Both are equally valid. The int puzzle[] form is however discouraged, the int[] puzzle is preferred according to the coding conventions. See also the official Java arrays tutorial:

Similarly, you can declare arrays of other types:

byte[] anArrayOfBytes;
short[] anArrayOfShorts;
long[] anArrayOfLongs;
float[] anArrayOfFloats;
double[] anArrayOfDoubles;
boolean[] anArrayOfBooleans;
char[] anArrayOfChars;
String[] anArrayOfStrings;

You can also place the square brackets after the array's name:

float anArrayOfFloats[]; // this form is discouraged

However, convention discourages this form; the brackets identify the array type and should appear with the type designation.

Note the last paragraph.

I recommend reading the official Sun/Oracle tutorials rather than some 3rd party ones. You would otherwise risk end up in learning bad practices.

Answer 11

It is an alternative form, which was borrowed from C, upon which java is based.

As a curiosity, there are three ways to define a valid main method in java:

• public static void main(String[] args)
• public static void main(String args[])
• public static void main(String... args)

Answer 12

There is no difference, but Sun recommends putting it next to the type as explained here

Answer 13

The most preferred option is int[] a - because int[] is the type, and a is the name. (your 2nd option is the same as this, with misplaced space)

Functionally there is no difference between them.

Answer 14

The Java Language Specification says:

The [] may appear as part of the type at the beginning of the declaration,
or as part of the declarator for a particular variable, or both, as in this
example:

byte[] rowvector, colvector, matrix[];

This declaration is equivalent to:

byte rowvector[], colvector[], matrix[][];

Thus they will result in exactly the same byte code.

Answer 15

In Java, these are simply different syntactic methods of saying the same thing.

Answer 16

They're the same. One is more readable (to some) than the other.

Answer 17

They are completely equivalent. int [] array is the preferred style. int array[] is just provided as an equivalent, C-compatible style.

Answer 18

There is no difference in functionality between both styles of declaration. Both declare array of int.

But int[] a keeps type information together and is more verbose so I prefer it.

Answer 19

Both have the same meaning. However, the existence of these variants also allows this:

int[] a, b[];

which is the same as:

int[] a;
int[][] b;

However, this is horrible coding style and should never be done.

Answer 20

They are the same, but there is an important difference between these statements:

// 1.
int regular, array[];
// 2.
int[] regular, array;

in 1. regular is just an int, as opposed to 2. where both regular and array are arrays of int's.

The second statement you have is therefore preferred, since it is more clear. The first form is also discouraged according to this tutorial on Oracle.

Answer 21

As already stated, there's no much difference (if you declare only one variable per line).

Note that SonarQube treats your second case as a minor code smell:

Array designators "[]" should be on the type, not the variable (squid:S1197)

Array designators should always be located on the type for better code readability. Otherwise, developers must look both at the type and the variable name to know whether or not a variable is an array.

Noncompliant Code Example

int matrix[][];   // Noncompliant
int[] matrix[];   // Noncompliant

Compliant Solution

int[][] matrix;   // Compliant

Answer 22

Yep, exactly the same. Personally, I prefer

int[] integers; 

because it makes it immediately obvious to anyone reading your code that integers is an array of int's, as opposed to

int integers[];

which doesn't make it all that obvious, particularly if you have multiple declarations in one line. But again, they are equivalent, so it comes down to personal preference.

Check out this page on arrays in Java for more in depth examples.

Answer 23

when declaring a single array reference, there is not much difference between them. so the following two declarations are same.

int a[];  // comfortable to programmers who migrated from C/C++
int[] a;  // standard java notation 

when declaring multiple array references, we can find difference between them. the following two statements mean same. in fact, it is up to the programmer which one is follow. but the standard java notation is recommended.

int a[],b[],c[]; // three array references
int[] a,b,c;  // three array references

Answer 24

Yes, there's a difference.

int[] a = new int[100]; // 'a' is not an array itself , the array is stored as an address elsewhere in memory and 'a' holds only that address

int b[] = new int[100]; // while creating array like cleary shows 'b' is an array and it is integer type.

Answer 25

Both are ok. I suggest to pick one and stick with it. (I do the second one)

Answer 26

While the int integers[] solution roots in the C language (and can be thus considered the "normal" approach), many people find int[] integers more logical as it disallows to create variables of different types (i.e. an int and an array) in one declaration (as opposed to the C-style declaration).