The Java Language Specification, Third Edition

BLOCKS AND STATEMENTS The assert Statement 14.10
DISCUSSION
Note that an assertion that is enclosed by a top-level interface does not cause initialization.
Usually, the top level class enclosing an assertion will already be initialized. However, if
the assertion is located within a static nested class, it may be that the initialization has nottaken
place.
A disabled assert statement does nothing. In particular neither Expression1
nor Expression2 (if it is present) are evaluated. Execution of a disabled assert
statement always completes normally.
An enabled assert statement is executed by first evaluating Expression1. If
the result is of type Boolean, it is subject to unboxing conversion (§5.1.8). If evaluation
of Expression1 or the subsequent unboxing conversion (if any) completes
abruptly for some reason, the assert statement completes abruptly for the same
reason. Otherwise, execution continues by making a choice based on the value of
Expression1 :
• If the value is true, no further action is taken and the assert statement completes
normally.
• If the value is false, the execution behavior depends on whether Expression2
is present:
◆ If Expression2 is present, it is evaluated.
❖ If the evaluation completes abruptly for some reason, the assert statement
completes abruptly for the same reason.
❖ If the evaluation completes normally, the resulting value is converted to a
String using string conversion (§15.18.1.1).
DRAFT
✣ If the string conversion completes abruptly for some reason, the assert
statement completes abruptly for the same reason.
✣ If the string conversion completes normally, an AssertionError
instance whose "detail message" is the result of the string conversion is
created.
✦ If the instance creation completes abruptly for some reason, the
assert statement completes abruptly for the same reason.
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