EXPRESSIONS

Compound Assignment Operators

15.25.2

At run time, the expression is evaluated in one of two ways. If the left hand

operand expression is not an array access expression, then four steps are required:

First, the left hand operand is evaluated to produce a variable. If this evalua 

tion completes abruptly, then the assignment expression completes abruptly

for the same reason; the right hand operand is not evaluated and no assign 

ment occurs.

Otherwise, the value of the left hand operand is saved and then the right hand

operand is evaluated. If this evaluation completes abruptly, then the assign 

ment expression completes abruptly for the same reason and no assignment

occurs.

Otherwise, the saved value of the left hand variable and the value of the right 

hand operand are used to perform the binary operation indicated by the com 

pound assignment operator. If this operation completes abruptly (the only

possibility is an integer division by zero see  15.16.2), then the assignment

expression completes abruptly for the same reason and no assignment occurs.

Otherwise, the result of the binary operation is converted to the type of the

left hand variable and the result of the conversion is stored into the variable.

If the left hand operand expression is an array access expression ( 15.12), then

many steps are required:

First, the array reference subexpression of the left hand operand array access

expression is evaluated. If this evaluation completes abruptly, then the assign 

ment expression completes abruptly for the same reason; the index subexpres 

sion (of the left hand operand array access expression) and the right hand

operand are not evaluated and no assignment occurs.

Otherwise, the index subexpression of the left hand operand array access

expression is evaluated. If this evaluation completes abruptly, then the assign 

ment expression completes abruptly for the same reason and the right hand

operand is not evaluated and no assignment occurs.

Otherwise, if the value of the array reference subexpression is

null

, then no

assignment occurs and a

NullPointerException

is thrown.

Otherwise, the value of the array reference subexpression indeed refers to an

array. If the value of the index subexpression is less than zero, or greater

than or equal to the length of the array, then no assignment occurs and an

IndexOutOfBoundsException

is thrown.

Otherwise, the value of the index subexpression is used to select a component

of the array referred to by the value of the array reference subexpression. The

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