Question: What are the main differences between Java and C++?

Answer: Everything is an object in Java( Single root hierarchy as everything gets derived from java.lang.Object). Java does not have all the complicated aspects of C++ ( For ex: Pointers, templates, unions, operator overloading, structures etc..)  The Java language promoters initially said "No pointers!", but when many programmers questioned how you can work without pointers, the promoters began saying "Restricted pointers." You can make up your mind whether it's really a pointer or not. In any event, there's no pointer arithmetic.
There are no destructors in Java. (automatic garbage collection), 
Java does not support conditional compile (#ifdef/#ifndef type).
Thread support is built into java but not in C++.
Java does not support default arguments.
There's no scope resolution operator :: in Java. Java uses the dot for everything, but can get away with it since you can define elements only within a class. Even the method definitions must always occur within a class, so there is no need for scope resolution there either.
There's no "goto " statement in Java.
Java doesn't provide multiple inheritance (MI), at least not in the same sense that C++ does.
Exception handling in Java is different because there are no destructors.
Java has method overloading, but no operator overloading.
The String class does use the + and += operators to concatenate strings and String expressions use automatic type conversion, but that's a special built-in case.
Java is interpreted for the most part and hence platform independent