Can you extend and implement at the same time in Java?
Yes, you can. But you need to declare extends before implements : public class DetailActivity extends AppCompatActivity implements Interface1, Interface2 { // } Any number of interfaces can be implemented, if more than one then each needs to be separated with a comma.
Can we extend and implement in same class?
A class can extend only one class; but can implement any number of interfaces. A subclass that extends a superclass may override some of the methods from superclass.
Can you implement and extend?
The keyword extends is used when a class wants to inherit all the properties from another class or an interface that wants to inherit an interface. We use the implements keyword when we want a class to implement an interface.
Why you can implement multiple interfaces but can extend only one class?
Since interfaces cannot have implementations, this same problem does not arise. If two interfaces contain methods that have identical signatures, then there is effectively only one method and there still is no conflict.
Can you implement multiple interfaces in Java?
Your class can implement more than one interface, so the implements keyword is followed by a comma-separated list of the interfaces implemented by the class. By convention, the implements clause follows the extends clause, if there is one.
When to Use implement and extend?
extends is used when you want attributes of parent class/interface in your child class/interface and implements is used when you want attributes of an interface in your class.
Can an interface extends a class just like a class implements interface?
No you can’t. An interface can extend another interface, but it can’t implement one. Only classes can implement interfaces.
Can we implement multiple interfaces with same method in Java?
If two interfaces contain a method with the same signature but different return types, then it is impossible to implement both the interface simultaneously. According to JLS (ยง8.4. 2) methods with same signature is not allowed in this case.
Why can’t we extend more than one class in Java?
When one class extends more than one classes then this is called multiple inheritance. For example: Class C extends class A and B then this type of inheritance is known as multiple inheritance. Java doesn’t allow multiple inheritance.
What will happen if a class extends two interfaces and they both have a method with same name and signature?
No, its an error If two interfaces contain a method with the same signature but different return types, then it is impossible to implement both the interface simultaneously.
What is the difference between the keywords extends and implement?
The extends keyword is mainly used to extend a class i.e. to create a subclass in Java, while the implements keyword is used to implement an interface in Java. The extends keyword can also be used by an interface for extending another interface.