Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs.

In contrast, threads can share class fields and instance fields because those variables do not allocate on a thread’s method-call stack.

Languages such as Java and Kotlin, which have a C and C++ heritage, use lower camel case for variables and methods, and upper camel case for reference types such as enums, classes and interfaces.