Can have instance mutable fields, parameters, or local variables. Only functional interfaces can use the lambda feature in Java. Abstract classes with only one abstract method cannot use lambdas.

This Java release effectively notified developers that it’s no longer sufficient to think about Java programming only from the imperative, ... (such as a Java instance variable).

This post explains how to use variables in Java. ... This is how variables work in programming. A variable is a label ... For instance, a constant is a variable whose value never changes.