Can interfaces be null?
Can interfaces be null?
Yes, it’s valid. It just means that delegate is a reference to ListAdapter interface and it’s currently pointing at null . You can later make it point to any class implementing the ListAdapter interface, such as SimpleCursorAdapter , WrapperListAdapter or any other implementation you want.
What is Serializable and cloneable interface in Java?
A serializable interface is used to persist an object. The cloneable interface is used to clone the class objects. Both these interfaces are marker interfaces i.e. they are empty. But when a class implements them, then they indicate that the compiler can expect some special behavior from the classes implementing them.
Is cloneable a marker interface?
Java has many built-in marker interfaces, such as Serializable, Cloneable, and Remote. Let’s take the example of the Cloneable interface.
Why is marker interface empty?
Marker interface is an empty interface where in doesn’t have any fields or methods in it. It is used to give some kind of command to jvm or a compiler. Example are Serializable, Clonnable etc.. When we implement empty interface, it tells compiler to do some operations.
Can we create object of interface?
Like abstract classes, interfaces cannot be used to create objects (in the example above, it is not possible to create an “Animal” object in the MyMainClass) Interface methods do not have a body – the body is provided by the “implement” class. On implementation of an interface, you must override all of its methods.
What is transient in Java?
transient is a Java keyword which marks a member variable not to be serialized when it is persisted to streams of bytes. When an object is transferred through the network, the object needs to be ‘serialized’. Serialization converts the object state to serial bytes.
Is serializable a marker interface?
The Serializable interface is present in java.io package. It is a marker interface. A Marker Interface does not have any methods and fields. Thus classes implementing it do not have to implement any methods.
What is clone () in Java?
The Java Object clone() method creates a shallow copy of the object. Here, the shallow copy means it creates a new object and copies all the fields and methods associated with the object. The syntax of the clone() method is: object.clone()
Why Serializable is a marker interface?
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. Implementing Serializable thus just tells the Java serialization classes that this class is intended for object serialization.
Is runnable a marker interface?
Runnable is not a Marker interface. AFAIK, Serializable, Clonable, SingleThreadModel, EventListener, RandomAccess, Remote are Marker Interfaces.