In the java language is this correct?

Question

Is this a proper way to initialize these variables

int x, sum;

Answer 1

this is variable declaration, without a assignment of value.

but integer is a primitive data type, with a default value (0)

Answer 2

yes, that is fine for java. it's good practice (IMO from days of C/C++) to initialize your variables when declared -- int x = 0, sum = 0 ; , but what you wrote is also technically correct.

Answer 3

no,this is a declaration, no an assignment of value.
an assignment is for exsample:

int x;
x = 10;

or

int x=10; <---- An Assignment and declaration

Integer is a primitive data type, with a default value (0)

Answer 4

if that variable is used in expressions wihtout getting assigned anywhere,

the javac throws this msg

The variable may not have been initialized.

Try this and understand.

All the Best.