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This is not necessarily true. The only rules for this are that interface methods may not be private. They may be public, protected, or have the default (blank) access modifier.
1.Implement the Listener interface and overrides its methods 2.Register the component with the Listener
It depends on how the class is declared.If the class is a normal class - Then the compiler will complain. All the methods in an interface must be implemented by the class to successfully compile the classIf the class is declared as abstract - Then the compiler will ignore the fact that a few methods are not implemented
Comparison between an Abstract Class and an Interface:While an abstract class can define both abstract and non-abstract methods, an interface can have only abstract methods. Another way interfaces differ from abstract classes is that interfaces have very little flexibility in how the methods and variables defined in the interface are declared. These rules are strict:
We can't instantiate both interfaces and abstract classes.The only one difference between them is that an interface can't contain concrete(fully defined) methods where as an abstract class may contain them.An abstract class not necessarily contain abstract methods. we can make a class as abstract class even it does not has any abstract methods.When there is a need to write both abstract and concrete methods in a single unit we have to use an abstract class instead of an interface since an interface cant contain concrete methods.All the fields(or properties) of an interface are by default 'static final' even when you don't mention explicitly. And all methods are 'public abstract'.But in an abstract class we can have any type of fields and methods.
The idea is that an interface is not a class, it is just a specification of what classes that implement it must contain.
An adapter class is a class that provides a dummy (empty) implementation for an interface. That way someone who wants to implement the interface but does not want or does not know how to implement all methods, can use the adapter class instead, and only override the methods he is interested in.
This is not necessarily true. The only rules for this are that interface methods may not be private. They may be public, protected, or have the default (blank) access modifier.
1.Implement the Listener interface and overrides its methods 2.Register the component with the Listener
It depends on how the class is declared.If the class is a normal class - Then the compiler will complain. All the methods in an interface must be implemented by the class to successfully compile the classIf the class is declared as abstract - Then the compiler will ignore the fact that a few methods are not implemented
In Java, an interface is a suite of methods that multiple different classes are able to implement. Interfaces are not assigned to any particular class. For example, multiple graphics classes can use the same interface to change their size and colour.
An Interface is nothing but a contract as to how a class should behave. It just declares the behavior as empty methods and the implementing class actually writes the code that will determine the behavior. When you implement an interface, you're agreeing to adhere to the contract defined in the interface. That means you're agreeing to provide legal implementations for every method defined in the interface, and that anyone who knows what the interface methods look like can rest assured that they can invoke those methods on an instance of your implementing class. (Thy need not bother much about how you have implemented it. All they bother about is whether a method of the name mentioned in the interface is available or not)
An interface is not a class. It is an entity that is defined by the word Interface. An interface has no implementation; it only has the signature, just the definition of the methods without the declaration(body). As one of the similarities to Abstract class, it is a contract that is used to define hierarchies for all subclasses or it defines specific set of methods and their arguments. Since C# doesn't support multiple inheritance, interfaces are used to implement multiple inheritance.
Comparison between an Abstract Class and an Interface:While an abstract class can define both abstract and non-abstract methods, an interface can have only abstract methods. Another way interfaces differ from abstract classes is that interfaces have very little flexibility in how the methods and variables defined in the interface are declared. These rules are strict:
While an abstract class can define both abstract and non-abstract methods, an interface can have only abstract methods. Another way interfaces differ from abstract classes is that interfaces have very little flexibility in how the methods and variables defined in the interface are declared. These rules are strict: • All interface methods are implicitly public and abstract. In other words, you do not need to actually type the public or abstract modifiers in the method declaration, but the method is still always public and abstract. (You can use any kind of modifiers in the Abstract class) • All variables defined in an interface must be public, static, and final-in other words, interfaces can declare only constants, not instance variables. • Interface methods must not be static. • Because interface methods are abstract, they cannot be marked final, strictfp, or native. (More on these modifiers later.) • An interface can extend one or more other interfaces. • An interface cannot extend anything but another interface. • An interface cannot implement another interface or class. • An interface must be declared with the keyword interface. You must remember that all interface methods are public and abstract regardless of what you see in the interface definition.
Externalizable interface is a subclass of Serializable. Java provides Externalizable interface so as to give you more control over what is being serialized and what is not. Using this interface, you can Serialize only the fields of the class you want serialize and ignore the rest. This interface defines 2 methods: readExternal() and writeExternal() and you have to implement these methods in the class that will be serialized. In these methods you'll have to write code that reads/writes only the values of the attributes you are interested in. Programs that perform serialization and deserialization have to write and read these attributes in the same sequence
A tagging interface type in Java is an interface that has not defined methods such as the java.io.Serializable interface.