use of { } in java while initializing as an array

Question

int[] outSize = new int[]{bytes, packets};

new byte[] {0, 0, 0, 0}

What does the first line of code mean? What is it doing to size array? How is the second line of code initializing that byte array (if it is at all)?

int [ ] outsize = new int[10].. i know what that does, but what is { } doing here?? — ABJ, Jun 17 '18 at 05:05
then bytes and packets are integers and they are initialized in outSize array — Sundeep, Jun 17 '18 at 05:11
https://stackoverflow.com/questions/11208479/how-do-i-initialize-a-byte-array-in-java i can see use of similar pattern here but dont know what it is? — ABJ, Jun 17 '18 at 05:12
please update your code currently its unclear what exactly you are not getting in the given code. — Sundeep, Jun 17 '18 at 05:20
That is simply the syntax to use when creating an array and providing the array entries directly. — GhostCat, Jun 17 '18 at 05:29

score 0 · Answer 1 · answered Jun 17 '18 at 05:35

We can initialized an array at the time of declaration using the given syntex

int[] outSize = new int[]{5, 9}; //create a Integer array of 2 element named outSize

OR

 int bytes = 5, packets =9;
 int[] outSize = new int[]{bytes, packets}; //create a Integer array of 2 element named outSize.

there is no difference using both the above statement.

score 0 · Answer 2 · answered Jun 17 '18 at 08:05

First line

int[] outSize = new int{ bytes, packets };

This creates an integer (primitive) array with two integer elements, namely bytes and packets.

Second line

new byte[] { 0, 0, 0, 0 }

By itself, this will give you an error (not compile) since it isn't a statement (there's no assignment to a variable anywhere).

If you write

byte[] bytes = new byte[] { 0, 0, 0, 0 };

you are declaring a byte array called bytes with four elements.

Use of {} for array initialization

Refer to chapter 10 (arrays) of the documentation, particularly sections 10.1 and 10.2.

Also worth reading, the primitive data types.

From the above:

int is a 32-bit signed two's complement integer (min value in base 10 is -2^31 and max is 2^31 - 1).

byte is an 8-bit signed two's complement integer (min value in base 10 is -2^7 and max is -2^7 - 1).

What it's doing

The first line uses 64 bits to store two integers.

The second line uses 32 bits to store four bytes.

2 Answers2