Java complains about final field not initialized in default case of a switch [duplicate]

Question

I want to initialize a final field in different ways. Therefore I have created an enumeration type and perform a switch over it.

 public enum TYPE { A, B, }

I have also added a default case to the switch with an assertion to warn my fellow programmers in case they add a new enumeration constant and forget to update the switch.

 default: assert false : "missing TYPE detected";

Java however detects the flaw in my argument and complains that the blank field may not have been initialized. How should I deal with this situation?

public class SwitchExample { public enum TYPE { A, B, } private final int foo; public SwitchExample(TYPE t) { switch (t) { case A: foo = 11; break; case B: foo = 22; break; default: assert false : "missing TYPE detected"; } // The blank final field foo may not have been initialized } }

then just initialize it in your default

Dmitry Zaytsev
– Dmitry Zaytsev

2013-04-09 09:10:40 +00:00
Commented Apr 9, 2013 at 9:10 — Dmitry Zaytsev
– Dmitry Zaytsev, Commented Apr 9, 2013 at 9:10

Xavier Delamotte · Accepted Answer · 2013-04-09 09:13:34Z

4

Instead of the assert false : "missing TYPE detected"; you may throw an IllegalArgumentException("missing TYPE detected")

answered Apr 9, 2013 at 9:13

Xavier Delamotte

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Gab · Accepted Answer · 2013-04-09 09:10:55Z

0

As you re-assign foo reference

foo = 11;

you cannot declare it as final

private final int foo;

See http://javarevisited.blogspot.fr/2011/12/final-variable-method-class-java.html

answered Apr 9, 2013 at 9:10

Gab

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3 Comments

Dmitry Zaytsev Over a year ago

You can assign value of a final variable inside constructor

Martin Wilson Over a year ago

You don't have to initialise a final variable at the point of declaration: en.wikipedia.org/wiki/Final_(Java)#Final_variables

Gab Over a year ago

Ok :) I learned something.

Dmitry Zaytsev · Accepted Answer · 2013-04-09 09:11:30Z

You can change code after your default to something like this:

assert (foo = 0) > 0 : "missing TYPE detected";

maloney · Accepted Answer · 2013-04-09 09:14:42Z

If using the final keyword you are forced to set its value in all cases in your switch statement. To get around this, just set your foo to a value you know means that an error has occured e.g. -1

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