Through interface, implicit class, inheritance, implementation and mutual cooperation, the effect of multiple inheritance is achieved.
1, a class in Java cannot inherit multiple concrete classes.
2. A class can only inherit from a specific class, but it can implement multiple interfaces.
The interface does not involve implementation details, nor does it involve any storage space.
You can merge multiple interfaces to achieve the purpose of upward conversion to multiple base classes.
A new class can inherit from a concrete class, and the rest of the inheritance must be an interface.
3. External classes cannot inherit from multiple concrete classes, but multiple internal classes can be provided internally, and each internal class can inherit an implementation class.
The inner class is not limited by whether the outer class inherits from the implementation class.
4. Inner classes can be said to be a complete solution to multiple inheritance problems.
An inner class can "inherit from multiple concrete or abstract classes".
A class cannot inherit from more than one regular class.