Can you extend interfaces in java

Collectives on Stack Overflow. Learn more. Ask Question. Asked 8 years ago. Active 1 year, 10 months ago. Viewed k times. Michael Prateek Prateek 6, 2 2 gold badges 22 22 silver badges 37 37 bronze badges. Which articles say it's not possible? They're either wrong, or you misunderstood them and they're talking about classes rather than interfaces. This question appears to be off-topic because it could easily be answered by self-research — JoseK. StephenC If he did find contradicting articles, he should post them.

That way people know not to read those articles The answer to this question saved me time. I argue that it has value as a valid question. Show 4 more comments. Active Oldest Votes. Yes, you can do it. Gurwinder Singh Suresh Atta Suresh Atta k 37 37 gold badges silver badges bronze badges.

RahulBhadana Abstract method should override right? What if you have interface A with void test and interface B with boolean test? Is this a cousin of the diamond problem? A class doesn't allow 2 methods same signature with different return type. Add a comment. An interface can extend multiple interfaces.

A class can implement multiple interfaces. However, a class can only extend a single class. Here we should first know the type of multiple inheritance in java:- Multiple inheritance of state. It is the mechanism in Java by which one class is allowed to inherit the features fields and methods of another class. In this article, the difference between extends and implements is discussed.

Before getting into the differences, lets first understand in what scenarios each of the keywords are used. Attention reader! Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. Extends: In Java, the extends keyword is used to indicate that the class which is being defined is derived from the base class using inheritance.

So basically, extends keyword is used to extend the functionality of the parent class to the subclass. In Java, multiple inheritances are not allowed due to ambiguity.

Therefore, a class can extend only one class to avoid ambiguity. Checked exceptions should not be declared on implementation methods other than the ones declared by the interface method or subclasses of those declared by the interface method. The signature of the interface method and the same return type or subtype should be maintained when overriding the methods. An implementation class itself can be abstract and if so, interface methods need not be implemented.

An interface can extend another interface in the same way that a class can extend another class. The extends keyword is used to extend an interface, and the child interface inherits the methods of the parent interface. The Hockey interface has four methods, but it inherits two from Sports; thus, a class that implements Hockey needs to implement all six methods. Similarly, a class that implements Football needs to define the three methods from Football and the two methods from Sports.

A Java class can only extend one parent class. Multiple inheritance is not allowed. Interfaces are not classes, however, and an interface can extend more than one parent interface. The extends keyword is used once, and the parent interfaces are declared in a comma-separated list. The most common use of extending interfaces occurs when the parent interface does not contain any methods. For example, the MouseListener interface in the java.

An interface with no methods in it is referred to as a tagging interface.