问从构造器调用阻塞方法- Java

EN

class A
{
    // Many instance variables that is to be initialized on instantiaion
    String tempVar = null;

    public A()
    {
        // Initialize all the instance variables
        tempVar=objectClassB.**callBlockingMethod**(); // this method call would return 
                                                       // some data from ClassB Object
    }

    public static void main(String args ...)
    {
        A a = new A();
        // Or should I call the blocking method call only after instantiation according
        // to any guidelines of Java pertaining to performance ?

        // IMPORTANT: It's only when the blocked method returns value , should the main
        // thread proceed as the object 'a' would be sent for further processing
    }
}