EXPRESSIONS

Evaluate Left Hand Operand First

15.6.1

A method invocation expression can also result in an exception being thrown if an

exception occurs that causes execution of the method body to complete abruptly.

A class instance creation expression can also result in an exception being thrown

if an exception occurs that causes execution of the constructor to complete

abruptly. Various linkage and virtual machine errors may also occur during the

evaluation of an expression. By their nature, such errors are difficult to predict and

difficult to handle.

If an exception occurs, then evaluation of one or more expressions may be ter 

minated before all steps of their normal mode of evaluation are complete; such

expressions are said to complete abruptly. The terms  complete normally 

and  complete abruptly  are also applied to the execution of statements ( 14.1).

A statement may complete abruptly for a variety of reasons, not just because an

exception is thrown.

If evaluation of an expression requires evaluation of a subexpression, abrupt

completion of the subexpression always causes the immediate abrupt completion

of the expression itself, with the same reason, and all succeeding steps in the nor 

mal mode of evaluation are not performed.

15.6   Evaluation Order

Let all things be done decently and in order.

 I Corinthians 14:40

Java guarantees that the operands of operators appear to be evaluated in a specific

evaluation order

, namely, from left to right.

It is recommended that Java code not rely crucially on this specification. Code

is usually clearer when each expression contains at most one side effect, as its

outermost operation, and when code does not depend on exactly which exception

arises as a consequence of the left to right evaluation of expressions.

15.6.1   Evaluate Left Hand Operand First

The left hand operand of a binary operator appears to be fully evaluated before

any part of the right hand operand is evaluated. For example, if the left hand oper 

and contains an assignment to a variable and the right hand operand contains a

reference to that same variable, then the value produced by the reference will

reflect the fact that the assignment occurred first.

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