The differences between abstract classes and interfaces in Java

1, abstract class represents a kind of is-a relationship, the interface is often expressed as a function. A class can only use one inheritance relationship at a time. But a class can implement multiple interfaces.

2, the abstract class has its own data members, you can also have their own non-abstract method, the interface can only have static data members can not be modified (that is, must be static final, but in interface generally do not define data members), all the member methods are abstract.

3, the implementation of the abstract class and interface class must implement all his methods, abstract classes can have non-abstract methods, interfaces can not be implemented by methods.

4, the method in the interface is the public abstract type by default.

5, the variables in the abstract class are friendly by default,

6, the variables in the interface are public static final, and must be assigned the initial value, the implementation class can not be redefined, and can not be re-assigned.

The differences between abstract classes and interfaces in Java