In this article, he dives into Local Variable Type Inference. Java SE 10 (March 2018) introduced type inference for local variables. Java Language Architect Brian Goetz explains the feature. BT.

There are three types of variables in Java: local variables, class variables or static variables, and instance variables or non-static variables. Local variables: Within the body of the method ...

Tip: Unlike class and instance field variables, threads cannot share local variables and parameters. The reason: Local variables and parameters allocate on a thread’s method-call stack.