multiple inheritance is prohibited because of a very simple reason. just imagine you have 2 super classes and one sub class inherting from above 2 superclasses. now suppose that both the superclass defines method with same signature i.e. same name and same number and type of arguments. now just think about it, which method out of 2 will subclass inherit. this is also called diamond of death.
in java a class cant extend 2 classes : because if same method same implementation is there in both which one will be inherited?but in java we allow a class to implement 2 interfaces? now can the same problem occur with interfaces? NO because interfaces dont have implemtation..so same problem not possible.