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For instance, when mapping objects to tables in a database at runtime, like Butterfly Persistence does. Or, when mapping the statements in a script language to method calls on real objects at runtime, like Butterfly Container does when parsing its configuration scripts.
va's static typing system isn't really designed to support this unless the object conforms to a known interface, but using reflection, your code can look at the object and find out if it has a method called 'doSomething' and then call it if you want to.
So, to give you a code example of this in Java (imagine the object in question is foo) :
Method method = foo.getClass().getMethod("
doSomethin g", null);
method.invoke(foo, null);One very common use case in Java is the usage with annotations. JUnit 4, for example, will use reflection to look through your classes for methods tagged with the @Test annotation, and will then call them when running the unit test.