Therefore, learning about variables in Java should be among the very first things you do when picking up the language. ... For instance, a constant is a variable whose value never changes.

Variable scope and lifetime. Developers implement instance variables to contain data useful to a class. An instance variable differs from a local variable in the nature of its scope and its lifetime.

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.

Instance main methods and unnamed classes are a preview feature in Java 21. Other Java 21 preview features preview features include the following: Unnamed patterns and variables. Scoped values.