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What is the point of an empty interface?
Empty interfaces can be checked at compile-time using the type-system in the compiler. This brings no overhead at runtime at all so it is faster.
Are marker interfaces better than annotations?
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. TYPE , it can be applied to any class or interface. Suppose you have a marker that is applicable only to implementations of a particular interface.
Can an interface extends another interface in Java?
An interface can extend other interfaces, just as a class subclass or extend another class. However, whereas a class can extend only one other class, an interface can extend any number of interfaces. The interface declaration includes a comma-separated list of all the interfaces that it extends.
Is serializable a marker interface?
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.
Why do you need marker interface in Java?
Java marker interface are useful if we have information about the class and that information never changes, in such cases, we use marker interface represent to represent the same. Implementing an empty interface tells the compiler to do some operations.
What is marker interface for?
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.
Is the empty interface a bad programming practice?
Are empty interfaces (but not marker interfaces) a bad programming practice? Generally, yes. By definition, empty interfaces provide you nothing. They can be marker interfaces (generally evil), or aliases for another type (occasionally useful due to legacy code when renaming something).
Is the marker interface a good or bad idea?
The marker interface is clever, which confounds users and creates a steep learning curve. Now, at this point, you might say that any design pattern has a learning curve, and that’s fair enough. When you have a truly sophisticated or elegant solution, that may create a learning curve worth the price tag.
Where did the marker interface come from in Java?
But the marker interface actually goes back a long way. In fact, it goes back to the earlier days of Java, which baked it in as a first class concept, kind of how C# contains a first class implementation of the iterator design pattern. In Java, concepts like serialize and clone came via marker interfaces.
Why is the customer interface a bad idea?
It has no behavior, so the idea of implementing it is nonsense. Instead, the customer class uses the interface to signify something to the client code using it. It marks itself as containing sensitive information, using the interface as a sort of metadata. Users of the class and marker interface then consume it with code resembling the following: