What is the meaning of i+=2 in Java programming language?

Assignment Operators

Same for: C/ C++/ Java/ JavaScript/ VB/ PHP and others.

Assignment operators are used to assigning the value of an expression to a variable. We have seen the usual assignment operator, '='. In addition, java has a set of shorthand assignment operators which are used in the form

v op= exp;

where v is a varible, exp is an expression and op is a java binary operator. The operator op= is known as the shorthand assignment operator.

v op= exp;

is equivalent to 

v = v op(exp);

with v accessed only once. consider an example:

x += y+1;

This is same as the statement

x = x+ (y+1);

The shorthand operator += means 'add y + 1 to x' or increment x by y+1 For y = 2. the above statement becomes
x += 3;
and when this statement is executed, 3 is added to x.

Statement with simple assignment operator	Statement with shorthand operator
a = a + 1	a +=  1
a = a -  1	a  -= 1
a = a * 1	a  * = 1
a = a / 1	a  /=  1
a = a % 1	a  %=  1