Full Answer
Can two interfaces have the same method?
So, if the class already has the same method as an Interface, then the default method from the implemented Interface does not take effect. However, if two interfaces implement the same default method, then there is a conflict.
What will happen if two interfaces have same default method?
If we are using more than one interface and in both interfaces, if both interfaces have the same name and same structure. So at that time, one must override either one both the default method otherwise it will result in an error.
What happens if two interfaces have same default method in Java?
Since Java allows classes to implement multiple interfaces, it's important to know what happens when a class implements several interfaces that define the same default methods. In this case, the code simply won't compile, as there's a conflict caused by multiple interface inheritance (a.k.a the Diamond Problem).
What to do if a class implements two interfaces which coincidentally have one method with the same name and signature?
If both interfaces have a method of exactly the same name and signature, the implementing class can implement both interface methods with a single concrete method.
CAN interface have 2 abstract methods?
And in any case, the specification says a functional interface cannot have more than one abstract method. So an interface with two abstract methods cannot be used by specification.
CAN interface have 2 default methods?
Multiple Defaults With default functions in interfaces, there is a possibility that a class is implementing two interfaces with same default methods.
Can we override default method in interface?
A default method cannot override a method from java. lang. Object . The reasoning is very simple, it's because Object is the base class for all the java classes.
CAN interface have private methods?
An interface can have private methods since Java 9 version. These methods are visible only inside the class/interface, so it's recommended to use private methods for confidential code. That's the reason behind the addition of private methods in interfaces.
Is it compulsory to override all methods of interface?
Yes, it is mandatory to implement all the methods in a class that implements an interface until and unless that class is declared as an abstract class.
What happens if you try to implement conflicting interfaces?
If we try to implement both interfaces in the same class then, it will throw an error.
Is it OK if a class definition implements two interfaces?
Is it OK if a class definition implements two interfaces, each of which has the same definition for the constant PI? a. No---if a class implements several interfaces, each constant must be defined in only one interface.
CAN interface have multiple static methods?
Since Java8 you can have static methods in an interface (with body). You need to call them using the name of the interface, just like static methods of a class.
Can you implement two interfaces with default method with same name and signature?
Classes can implement more than one interface. As interface can consist of default methods in Java 8, which a class does not necessarily need to implement. We can have two interfaces that have default methods with the same name and signature.
Can default methods be specified in both classes and interfaces?
In case both the implemented interfaces contain default methods with same method signature, the implementing class should explicitly specify which default method is to be used or it should override the default method.
How do you resolve default method conflicts in interface?
Rules for Default Method Conflict Resolution Classes will always win. If a class extends a parent class and implements one or more interfaces, the default method in the class or a superclass will take priority. Otherwise the subinterfaces will take the next level of precedence.
What does a default do to interface?
Default methods are methods that can have a body. The most important use of default methods in interfaces is to provide additional functionality to a given type without breaking down the implementing classes. Before Java 8, if a new method was introduced in an interface then all the implementing classes used to break.
What happens if two methods have conflicting return types?
If, say, the two methods have conflicting return types, then it will be a compilation error. This is the general rule of inheritance, method overriding, hiding, and declarations, and applies also to possible conflicts not only between 2 inherited interface methods, but also an interface and a super class method, or even just conflicts due to type erasure of generics.
Is it a problem if two methods are identical?
This isn't a problem if the two methods are effectively identical, in that they should have the same implementation. If they are contractually different (as per the documentation for each interface), you'll be in trouble.
Can you define methods in concrete class?
As in interface,we are just declaring methods,concrete class which implements these both interfaces understands is that there is only one method (as you described both have same name in return type). so there should not be an issue with it.You will be able to define that method in concrete class.
Can you have two interfaces with the same name but different return type?
In this way, you will not be able to implement two interface having a method of same name but different return type.
Does the compiler have to identify which method is for which interface?
The compiler does not have to identify which method is for which interface, because once they are determined to be @Override -equivalent, they're the same method.
Can you inherit a method that is @override equivalent?
You can inherit methods that are @Override -equivalent, subject to the usual requirements of method overriding and hiding. Since they ARE @Override -equivalent, effectively there is only one method to implement, and thus there's nothing to distinguish/select from.
Can you implement two interfaces in a single class?
However, if the semantic contracts of the two interface method are contradicting, you've pretty much lost; you cannot implement both interfaces in a single class then.
When using explicit interface implementations, the functions are not public on the class?
Therefore in order to access these functions, you have to first cast the object to the interface type, or assign it to a variable declared of the interface type.
Is an interface always public?
Methods/properties on an interface are always public - that is the entire point of an interface. But when you use an explicit interface implementation, the function will always be private on the class. That is why you need the technique to cast the class to the specific interface that you need. When you do implement two interfaces that define methods with identical signature, you cannot avoid this.
Can you implement one interface explicitly and another implecitely?
You can implement one interface Explicitlyand another implecitely.
Can you implement both interfaces?
You can implement one or both of those interfaces explicitly.
