dynamic typing : Java Glossary

dynamic typing

Java is a statically typed language. In a dynamically typed language, typically:

Variables do not have type constraints on them. They are generic and can point to anything.
The identity of method calls, a.k.a. messages can be computed and manipulated at run-time, and then an object (reference) plus this message value combined to make a call. Matt Kennel would call this dynamic messaging.
Note, this is not polymorphism in the standard OO (Object Oriented) sense. There, the identity of the specific subroutine is computed at runtime with a combination of the run-time-varying specific type, plus the statically known method call name.

Imagine this: in a dynamically typed language, you could pop off three stacks: object reference, message reference, arguments, mix them, and call the result.
Occasionally (in some research languages) dynamic typing means the identity of 'which type is some object' is computed as a user-defined predicate upon its run-time varying data, and is not an invariant of its creation. The object’s type may mutate, perhaps as it acquires additional fields.

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