About Question enthuware.ocpjp.v7.2.1223 :

[sinapse]

Hi,
why the compiler is not capable to understand that the String is null, even before it calls String.equals() ?

Thanks

[admin]

1. Compiler takes only the values of compile time constants into consideration while generating errors. In this case, str is a variable and so it ignores it value.
2. Compiler doesn't execute any code so it doesn't really "know" the value of a variable.

HTH,
Paul.

[hamada.yamasaki]

But if we have

Code: Select all

 final String str = null ;

then why still compiler compiles the code?

[admin]

Hamada, the compiler knows that str is null in your example but I am not sure why you think that it should not compile. null check happens at run time. So there is no reason for a compilation error here.

[hamada.yamasaki]

You are right , I mixed some other question. Thanks for your time.