A normal class can implement any number of interfaces but anonymous inner class can implement only one interface at a time. A regular class can extend a class and implement any number of interface simultaneously. But anonymous Inner class can extend a class or can implement an interface but not both at a time..
Also know, can an interface have an inner class?
Yes, you can create both a nested class or an inner class inside a Java interface (note that contrarily to popular belief there's no such thing as an "static inner class": this simply makes no sense, there's nothing "inner" and no "outter" class when a nested class is static, so it cannot be "static inner").
what is the use of inner interface in Java? An interface which is declared inside another interface or class is called nested interface. They are also known as inner interface. Since nested interface cannot be accessed directly, the main purpose of using them is to resolve the namespace by grouping related interfaces (or related interface and class) together.
Subsequently, one may also ask, can we have interface inside interface in Java?
Nested Interface in Java. We can declare interfaces as member of a class or another interface. Such an interface is called as member interface or nested interface. Interfaces (or classes) can have only public and default access specifiers when declared outside any other class (Refer this for details).
What is an anonymous inner class?
An inner class declared without a class name is known as an anonymous inner class. In case of anonymous inner classes, we declare and instantiate them at the same time. Generally, they are used whenever you need to override the method of a class or an interface.
Related Question Answers
Can interface extends class?
Java interfaces cannot extend classes, which makes sense since classes contain implementation details that cannot be specified within an interface.. If you want to share code among all Vehicle instances, then you can use a (possibly abstract) class as a parent for any classes that need to implement that interface.Why interface variables are static and final?
Interface variables are static because Java interfaces cannot be instantiated on their own; the value of the variable must be assigned in a static context in which no instance exists. The final modifier ensures the value assigned to the interface variable is a true constant that cannot be re-assigned by program code.What is nested interface?
An interface which is declared inside another interface or class is called nested interface. They are also known as inner interface. Since nested interface cannot be accessed directly, the main purpose of using them is to resolve the namespace by grouping related interfaces (or related interface and class) together.Why interface methods are not protected?
2 Answers. Protected methods are intended for sharing implementation with subclasses. Interfaces have nothing to offer as far as implementation sharing goes, because they have no implementation at all. Therefore all methods on interfaces must be public.Can a class have interface in Java?
An interface is just like Java Class, but it only has static constants and abstract method. Java uses Interface to implement multiple inheritance. A Java class can implement multiple Java Interfaces. To use an interface in your class, append the keyword "implements" after your class name followed by the interface name.What is inner class in Java?
Java inner class or nested class is a class which is declared inside the class or interface. We use inner classes to logically group classes and interfaces in one place so that it can be more readable and maintainable.Can we declare static method in interface?
Static Methods in Interface are those methods, which are defined in the interface with the keyword static. Similar to Default Method in Interface, the static method in an interface can be defined in the interface, but these methods cannot be overridden in Implementation Classes.How do you create an interface in Java?
Java uses Interface to implement multiple inheritance. A Java class can implement multiple Java Interfaces. All methods in an interface are implicitly public and abstract. To use an interface in your class, append the keyword "implements" after your class name followed by the interface name.What is the difference between abstract class and interface?
Main difference is methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can have instance methods that implements a default behavior. Variables declared in a Java interface is by default final. An abstract class may contain non-final variables.What is functional interface in Java?
A functional interface is an interface that contains only one abstract method. They can have only one functionality to exhibit. From Java 8 onwards, lambda expressions can be used to represent the instance of a functional interface. Runnable, ActionListener, Comparable are some of the examples of functional interfaces.What does interface mean in Java?
An interface is a reference type in Java. It is similar to class. It is a collection of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface. Along with abstract methods, an interface may also contain constants, default methods, static methods, and nested types.WHAT IS interface in Java with example?
Interfaces in Java. Like a class, an interface can have methods and variables, but the methods declared in an interface are by default abstract (only method signature, no body). Interfaces specify what a class must do and not how. It is the blueprint of the class. A Java library example is, Comparator Interface.Can an interface implement another interface C#?
C# | Inheritance in interfaces. C# allows the user to inherit one interface into another interface. When a class implements the inherited interface then it must provide the implementation of all the members that are defined within the interface inheritance chain.Can we define private and protected modifiers for variables in interfaces?
3 Answers. as you have declare variable in test interface with private and protected it will give error. if you do not specify the modifier the compiler will add public static final automatically. Having private or protected members in an interface doesn't make sense conceptually.What is abstract class in Java?
Java Abstract Classes and Methods Abstract class: is a restricted class that cannot be used to create objects (to access it, it must be inherited from another class). Abstract method: can only be used in an abstract class, and it does not have a body. The body is provided by the subclass (inherited from).How can we achieve inheritance in Java?
In Java inheritance is declared using the extends keyword. You declare that one class extends another class by using the extends keyword in the class definition. Here is Java inheritance example using the extends keyword: In java, it is possible to reference a subclass as an instance of one of its super-classes.How do I access static nested class?
And like static class methods, a static nested class cannot refer directly to instance variables or methods defined in its enclosing class: it can use them only through an object reference. They are accessed using the enclosing class name. To instantiate an inner class, you must first instantiate the outer class.WHAT IS interface in Java Javatpoint?
An interface in Java is a blueprint of a class. It has static constants and abstract methods. The interface in Java is a mechanism to achieve abstraction. There can be only abstract methods in the Java interface, not method body. It is used to achieve abstraction and multiple inheritance in Java.What is package in Java with example?
Package in Java is a mechanism to encapsulate a group of classes, sub packages and interfaces. Packages are used for: Preventing naming conflicts. For example there can be two classes with name Employee in two packages, college. 
