What is the main difference in object creation between Java and C++?

Question

I\'m preparing for an exam in Java and one of the questions which was on a previous exam was:\"What is the main difference in object creation between Java and C++?\"

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Answer 1

There is one main design difference between constructors in C++ and Java. Other differences follow from this design decision.

The main difference is that the JVM first initializes all members to zero, before starting to execute any constructor. In C++, member initialization is part of the constructor.

The result is that during execution of a base class constructor, in C++ the members of the derived class haven't been initialized yet! In Java, they have been zero-initialized.

Hence the rule, which is explained in paercebal's answer, that virtual calls called from a constructor cannot descend into a derived class. Otherwise uninitialized members could be accessed.