This article is also part of my book Java Coding Problems.
The Java Local Variable Type Inference (LVTI), or shortly, the var type (the identifiervaris not a keyword, is a reserved type name), was added in Java 10 via JEP 286: Local-Variable Type Inference. As a 100 percent compile feature, it doesn't affect bytecode, runtime, or performance. Mainly, the compiler will inspect the right-hand side and infer the concrete type. It looks at the right-hand side of the declaration, and if there is an initializer, then it simply uses that type to replacevar. Addtionally, it is useful to reduce verbosity, redundancy, and boilerplate code. It is also meant to speed up the ceremonies involved while writing code. For example, it is very handy to writevar evenAndOdd =...instead of Map <Boolean, List <Integer>> evenAndOdd.... Depending on the use case, it has a trade-off in code readability that is covered in the first item below.