Local variable type inference: Friend or foe?
summary
Local variables use type inference introduced in Java SE 10 so the compiler fixes the type at declaration and JDK 11 adds lambda parameter var for annotated params. Examples show concrete pitfalls: array initializers fail with var, var forbids uninitialized and null assignments, using the diamond with var backfires because diamond plus var infers Object and primitive literals often become int which can flip logic in bitmasking so primitive literals infer int causing wrong behavior. Use var for local constructors and chained expressions only when the initializer makes the type obvious.
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chapters (19)
- 0:00Intro
- 3:30Why add it to Java
- 6:22Simple uses
- 8:06Using var
- 10:20Try with resources
- 12:02Variable type inference
- 13:34Making a variable final
- 15:36Action of the distance
- 17:11Jumping variable names
- 18:37Edge cases
- 20:14Null
- 21:46Types
- 23:50Use of literals
- 26:23Use of diamond operator
- 28:11var
- 33:29lambda parameters
- 35:43intersection types
- 40:21audience question
- 46:43guidelines
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