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Why isn't a final variable always a constant expression?

java,expression,constants,compile-time-constant,narrowing
In the below code: final int a; a=2; byte b=a; // error: possible loss of precision Why do I get this error? Isn't a final variable compile time constant expression and hence implicitly narrowed to byte during the assignment? In other words isn't the above code equivalent to: final int...

Narrowing conversion of '65280' from 'int' to 'short int' inside { }

c++,int,short,narrowing
I have two arrays: short GMobiles[18] = {0x0000, 0x0001, 0x0002, 0x0003, 0x0004, 0x0005, 0x0006, 0x0007, 0x0008, 0x0009, 0x000A, 0x000B, 0x000C, 0x000D, 0x000E, 0x000F, 0x00FF, 0xFFFF}; short GMobiles2[18] = {0xFF00, 0xFF01, 0xFF02, 0xFF03, 0xFF04, 0xFF05, 0xFF06, 0xFF07, 0xFF08, 0xFF09, 0xFF0A, 0xFF0B, 0xFF0C, 0xFF0D, 0xFF0E, 0xFF0F, 0xFFFF, 0xFFFF}; When I compile, I...

Optional<> and return type narrowing

java,optional,narrowing
In Java < 8, returning "unsafe" objects (objects or null), I was able to specialize return type in subclass: class A {} class B extends A {} interface Sup { A a(); /* returns A instance, or null */ } interface Sub extends Sup { B a(); } In Java...