Java Practices->Assertions in general

Assertions in general

Assertions in general:

when an assertion is fired, pass the offending piece of data to AssertionError
the checks performed inside an assertion are usually simple boolean conditions - side effects are usually to be avoided
since assertions can be disabled, the behaviour of a program must not depend upon assertions being executed
if desired, the conditional compilation idiom can still be used
you can almost always ignore the methods in ClassLoader regarding assertions - they are intended for interpreters such as java, and are not used in a typical program

Reminders regarding use :

at runtime, assertions are disabled by default
the -enableassertions and -disableassertions runtime parameters (or their synonyms -ea and -da) control assertions to any degree of granularity
AssertionError behaves as any other Error, and is not affected by enabling or disabling of assertions.
to compile code containing assertions, older JDKs need to add -source 1.4 as a command line argument to javac

Examples of typical styles, which affect non-system classes:

Runtime command line	Classes with assertions enabled
java -ea Main	all classes
java -ea:com.Blah Main	one particular class named `Blah`
java -ea:com.data... Main	all classes in the com.data package, and all of its sub packages
java -ea -da:com.Blah Main	all but one class named `Blah`