Marker interface in java

The marker interface in Java is used to provide additional information about classes at runtime. Marker interfaces, like the Serializable interface, can be used by the JVM to perform certain actions or optimizations based on the interface’s presence. This is important because it allows for more precise control over how classes are treated by the JVM and enables new capabilities, such as serialization and remote method. What is Marker Interface The marker interface in Java is an empty interface that does not contain any methods or fields. It is simply a way to mark or flag a class as having a specific characteristic or behavior. When a class implements a marker interface, it signals to the compiler or the runtime environment that the class has the desired behavior associated with the marker interface. This provides a flexible way to add behaviour to classes without actually adding any functionality to them. Examples of Marker interface in java include Serializable, Cloneable, and Remote, among others. Syntax of Marker Interface in Java public class MyClass implements MarkerInterfaceName Example of Serializable: import java.io.*; public class MyClass implements Serializable Example for Cloneable: public class MyClass implements Cloneable Example for Remote: import java.rmi.Remote; import java.rmi.RemoteException; public interface MyRemoteInterface extends Remote Explanation of annotations in java In this example, we define an annotation MyAnnotation with two elements, na...

A marker interface is basicaly empty, containing no methods or constants. It is used to merely indicate (at runtime) that the class implementing such an interface has some special property or attributes. These are sometimes known as “tag” or “placeholder” interfaces. Examples: Serializable and Cloneable. Implementing marker interfaces don’t make the object do more, rather it just says what it can do. For example, let’s consider Cloneable. It’s a marker interface that contains no methods. protected Object clone () throws CloneNotSupportedException Similarly, ObjectOutputStream.writeObject(Object obj) method checks if the object (passed as argument) implements the Serializable (marker) interface. If the answer is no, a NotSerializableException is thrown at runtime. If instead, the argument to writeObject(...) was of type Serializable, the check could have been performed at compile-time. But as it stands, any attempt to serialize an unserializable object will not fail until runtime. Annotations Annotations were introduced later in Java as a way to reduce boiler plate code. They were considered an improvement over marker interfaces, developers calling them “Marker Interfaces 2.0” or “Marker Interfaces++”. However’ as we’ll explore later, annotations don’t make marker interfaces obsolete and both have their advantages and disadvantages. We are all familiar with annotation and seen them everywhere: @Override, @FunctionalInterface, @Deprecated, etc. Annotation have many use case...

package java.io ; public interface Serializable A class implements this interface to indicate that its non- ObjectOutputStream private method writeObject0(Object,boolean) contains a series of instanceof tests to determine writeability, one of which looks for the Serializable interface. If any of these tests fails, the method throws a NotSerializableException. Critique [ ] A major problem with marker interfaces is that an interface defines a contract for implementing classes, and that contract is inherited by all subclasses. This means that you cannot "unimplement" a marker. In the example given, if you create a subclass that you do not want to serialize (perhaps because it depends on transient state), you must resort to explicitly throwing NotSerializableException (per ObjectOutputStream docs) Another solution is for the language to support • Both the "custom attributes", in Java they are called " • In implementsOnly to declare they do not implement everything from their super classes. See also [ ] • References [ ]

In this tutorial, we will learn one of the very basic and important concepts in Java that is what is marker interface in Java and what are the examples of marker interfaces in Java. Let’s start the tutorial. Overview to What are Marker Interface in Java The marker interface is an empty interface ( with no fields and methods inside it). This is the basic definition of marker interface in Java. Now next important question is what the examples of marker interface are. Serializable, Cloneable, and Remote interfaces are the best example of Marker interfaces. Below is the sample code snippet of the Serializable interface. public interface Serializable 100 Codezup.com After these two interfaces, the next marker interface is the Remote interface in Java. Let’s discuss this. Remote Interface in Java First, we will understand what is a Remote object? A remote object is an object which is stored at one machine and can be accessed from another machine. To make an object a remote object we need to flag it with the Remote interface. Simply we can say that any object that is a remote object must implement the Conclusion That’s all for this tutorial. Hope you like the tutorial and are able to understand the marker interface concept in Java. Please share this tutorial with others if you find this informative and comment on your thoughts in the comment section down below. Happy Learning. • Click to share on Facebook (Opens in new window) • Click to share on Twitter (Opens in new window) • ...

Serialization is a mechanism of converting the state of an object into a byte stream. Deserialization is the reverse process where the byte stream is used to recreate the actual Java object in memory. This mechanism is used to persist the object. The byte stream created is platform independent. So, the object serialized on one platform can be deserialized on a different platform. To make a Java object serializable we implement the java.io.Serializable interface. The ObjectOutputStream class contains writeObject() method for serializing an Object. public final void writeObject(Object obj) throws IOException The ObjectInputStream class contains readObject() method for deserializing an object. Only the objects of those classes can be serialized which are implementing java.io.Serializable interface. Serializable is a marker interface (has no data member and method). It is used to “mark” java classes so that objects of these classes may get certain capability. Other examples of marker interfaces are:- Cloneable and Remote. Points to remember 1. If a parent class has implemented Serializable interface then child class doesn’t need to implement it but vice-versa is not true. 2. Only non-static data members are saved via Serialization process. 3. Static data members and transient data members are not saved via Serialization process. So, if you don’t want to save value of a non-static data member then make it transient. 4. Constructor of object is never called when an object is des...

• Cloneable interface : Cloneable interface is present in java.lang package. There is a method clone() in Invoking Object’s clone method on an instance of the class that does not implement the Cloneable interface results in an exception CloneNotSupportedException being thrown. By convention, classes that implement this interface should override Object.clone() method. Refer Output: 20 GeeksForGeeks• Serializable interface : Serializable interface is present in java.io package. It is used to make an object eligible for saving its state into a file. This is called Classes that do not implement this interface will not have any of their state serialized or deserialized. All subtypes of a serializable class are themselves serializable. 20 GeeksForGeeks• Remote interface : Remote interface is present in java.rmi package. A remote object is an object which is stored at one machine and accessed from another machine. So, to make an object a remote object, we need to flag it with Remote interface. Here, Remote interface serves to identify interfaces whose methods may be invoked from a non-local virtual machine.Any object that is a remote object must directly or indirectly implement this interface. RMI ( This article is contributed by Gaurav Miglani. If you like GeeksforGeeks and would like to contribute, you can also write an article using Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

prog.java:28: error: incompatible types: Object cannot be converted to Student Student s2 = s1.clone(); ^ 1 error Example 2: Below code explains the proper usage of the Cloneable interface to make the Object.clone() method legal. Classes that implement this interface should override the Object.clone() method (which is protected) so that it can be invoked. Output 20 GeeksForGeeks Deep Copy using clone() method Deep Object Cloning is like creating an exact copy of the original object by copying the fields from the original object to the cloned object. A separate memory is allocated for the cloned objects where the original object content is copied. deep copy of the original object based on the implementation of it. Deep copy creates a new memory with the contents same as the original object. That’s why when we change the content of the original object after cloning, the changes do not reflect in the clone object. There are types of copies such as Output 10 20 30 40 100 20 300 0 Note: This interface does not contain the clone method. Therefore, it is not possible to clone an object merely by virtue of the fact that it implements this interface. Even if the clone method is invoked reflectively, there is no guarantee that it will succeed. Reference: