The final keyword is not redundant—quite the opposite—it's extremely valuable.
Local variables are not, in general, final, unless you declare them as such. That being the case, it is not redundant to declare local variables "final". What the compiler will do for you, is _if_ it can ensure that a local variable (or method parameter) is never modified (after initialization) then that variable is treated as "effectively final". Variables that are explicitly declared final, or are determined to be "effectively final" may be referenced in lambdas. That's a nice thing. I would like to offer a counter-recommendation: *final should be the default everywhere for fields, for method parameters (on classes, not on interfaces), and for local variables*. Many benefits would accrue to us, should we adopt this default: 1. final fields must be initialized in a constructor and never mutated again. This makes reasoning about those fields easier. 2. classes that have all their fields final are immutable and hence easier to reason about: they can be passed between threads, for instance, with no need to protect from races 3. final method parameters can never be mutated, making them easier to reason about 4. final local variables can never be mutated, making them easier to reason about When final is the rule, non-final is the exception. Another way of saying that is that when final is the rule, mutability is the exception. That is as it should be. *Mutability is the enemy*. I have turned on a couple IntelliJ settings that make this the default for me. I encourage you to do the same: First there are these two "Code style issues" in the Java inspections: "Field may be 'final'" "Local variable or parameter can be final" [image: image.png] Then there is this setting will cause newly-defined variables created via the "Extract variable" refactoring: If you select that check box (after selecting those inspections settings above), it'll declare the newly-introduced variable "final" and it'll remember the setting the next time you invoke "Extract variable" refactoring [image: image.png]
