This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Multiple inheritance can be a serious mess and has been a point of contention in the C++ world, therefore Java has removed the notion of multiple inheritance. However, you can implement multiple interfaces.
The secret to creativity is knowing how to hide your sources.
Do you mean multiple inheritance? If so, preventing multiple inheritance avoids many of the associated problems such as where D extends B and C both of which extend A. If you call a method on D which is implemented in B and C, which implementation do you choose? Multi level inheritance (e.g. C extends B extends A) is allowed.