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My question is mainly about performance. The compiler knows better that, for example, some variable is NOT modified after object instantiation. So, why bother with final?
I presume many structural/logical reasons might come here, but speaking from the performance point of view? Does it matter?
Thanks,
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A final field is one that cannot be changed once it is initialized. This means slightly different things for primitive and class types.
In Java, the final keyword can be used while declaring an entity. Using the final keyword means that the value can't be modified in the future. This entity can be - but is not limited to - a variable, a class or a method.
the reader of the code need not to reason at all about the value of a final variable (except for rare bad-code cases). So, yes, it's a good practice.
Java For TestersA variable cannot be modified after it is declared as final. In other words, a final variable is constant. So, a final variable must be initialized and an error occurs if there is any attempt to change the value.
In a modern JVM, final shouldn't affect performance. This is especially true for private fields, but even for non-private fields the JIT can optimize non-final fields as thought they are final, and then deoptimize if it loads some code that actually does modify the field.
That said, the main reason to use final is not performance, but to make your code more maintainable. By making fields final you are reducing the number of "moving parts" readers of your code have to think about, making it much easier to reason about the code.
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