Question

The following is a translation of an atomic wait in Java.
Here what is the need for while? Isn’t if sufficient?

///<await (condition) statements; > 

synchronized(obj)
{ 
      while ( !condition) 
      { 
         obj.wait();
      }
      statements;
}

Answer 1

You need the while, because just because someone sent you a notify does not mean that the condition is now true (or is still true).

All notify does (or is supposed to do) is tell the waiting threads (of which there can be many, with different conditions to wait for, even on the same monitor) that now would be a good time to re-evaluate if they still need to wait.