Quick Answer: Why Marker Interface Has No Method?

Is serializable a marker interface?

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Serializable is a marker interface your classes must implement if they are to be serialized and deserialized.

That Serializable is a marker interface means that it contains no methods.

Therefore, a class implementing Serializable does not have to implement any specific methods..

How does a marker interface work internally?

A marker interface is an interface that has no methods or constants inside it. It provides run-time type information about objects, so the compiler and JVM have additional information about the object. A marker interface is also called a tagging interface.

Which of the following is not a marker interface?

2. Which of the following is not a marker interface? Explanation: Reader is not a marker interface. Serializable, Cloneable and Remote interfaces are marker interface.

Are marker interfaces better than annotations?

Marker interfaces define a type that is implemented by instances of the marked class; marker annotations do not. … Another advantage of marker interfaces over marker annotations is that they can be targeted more precisely. If an annotation type is declared with target ElementType.

What is the purpose of marker interface?

It is also known as a tagging interface and is used to indicate or inform the JVM that a class implementing this interface will have some special behaviour. An efficient way to classify code can be achieved using the marker interface. Examples of such an interface are: Serializable, Cloneable and Remote Interface.

How do you create a marker interface?

We can create our own marker interface, but it has nothing to do with JVM, we can add some checks with instanceOf .Create the empty interface interface Marker{ }Write a class and implements the interface class A implements Marker { //do some task }More items…•

What can we use instead of marker interface?

In modern Java, marker interfaces have no place. They can be completely replaced by Annotations, which allow for a very flexible metadata capability. If you have information about a class, and that information never changes, then annotations are a very useful way to represent it.

Can an interface be empty?

An empty interface in Java is known as a marker interface i.e. it does not contain any methods or fields by implementing these interfaces a class will exhibit a special behavior with respect to the interface implemented. java. lang. Cloneable and java.

Can marker interface have methods?

A marker interface in Java is an interface with no fields or methods. Put more simply, an empty interface in Java is called a marker interface. Examples of marker interfaces are the Serializable , Cloneable and Remote interfaces. … So if the JVM sees that a class is Serializable , it can do some special operation on it.

Is it necessary to define 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. … Declare the class as an abstract class, as a result, forces you to subclass the class (and implement the missing methods) before you can create any objects.

Is Externalizable a marker interface?

Difference between Serializable and Externalizable in Java 1) One of the obvious difference between Serializable and Externalizable is that Serializable is a marker interface i.e. does not contain any method but Externalizable interface contains two methods writeExternal() and readExternal().

Is runnable marker interface?

Runnable interface is not marker because Runnable interface has the public void run() method declared inside it. A very good example of marker interface is Serializable where the class implements can be used with ObjectOutputStream and ObjectInputStream classes.