inheritance - Making variable volatile in subclass, in Java -

i've come across following situation:

public class foo {     private boolean valid;         ... }  public class concurrentfoo extends foo {         ... } 

since concurrentfoo subclass used in multithreaded environment, opposed foo, not thread-safe, i'd boolean valid be, instead, volatile boolean valid, only in subclass.

the goal using volatile avoid locks , synchronization, since seem unnecessary. there ever 2 updates variable in lifetime of object, , lots of (concurrent) reads.

of course, use synchronization solve problem in subclass, or implement other way, such there clearer distinction when using foo , concurrentfoo. instance:

public class concurrentfoo extends foo {     // considered shadowing, when adding volatile?     private volatile boolean valid;     // or fresh name.     private volatile boolean concurrentvalid; } 

anyway, i curious know if possible modify non-access modifiers, such volatile (well, except final), in subclass.

if isn't possible, , think may not be, unless shadowing alternative considered, what simplest way overcome situation?
synchronization in subclass?

do tell, if more context needed.
should note performance of relevance in case.

i suspect not making volatile premature optimization. if don't need volatile, made volatile, wasting 3-10 nano-seconds. if call 100 times wasting micro-second (over life of component suspect). amount of time critical you?