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What happens if a class doesn't implement all the methods defined in the interface?
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 class
- If the class is declared as abstract - Then the compiler will ignore the fact that a few methods are not implemented
What else can I help you with?
What Java interface do you implement to provide methods that are called as an XML document is processed by a SAX parser?
ContentHandler
Abstract class vs interface?
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:
What does implementation mean in java?
Implementation in java mean to accomplish some aim or to execute some order in java software platform. Your class can implement more than one interface, so the implements keyword is followed by a comma with separated list of the interfaces implemented by the class. By convention, the implements clause follows the extends clause, if there is one.
Why use interfaces in Java?
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) Now, you might stop me and ask, what if I implement an interface and opt not to write code for a method that I am supposed to? The answer is simple. The compiler wouldn't let you do that. You cannot successfully implement an interface without providing method implementation for all the methods declared inside the interface. This is how the java system ensures that when someone knows a certain method name in an interface and has an instance of a class that implements it, can actually call that method without fear that the method isnt implemented inside the class. Assuming an interface, Convertible, with two methods: openHood(), and setOpenHoodFactor(), the following class will compile: public class Ball implements Convertible { // Keyword 'implements' public void openHood() { } public void setOpenHoodFactor(int bf) { } } Ok, I know what you are thinking now. "This has got to be the worst implementation class that you have seen". Though it compiles and runs as well, it is actually doing nothing… the interface contract guarantees that the class implementing it will have a method of a particular name but it never guaranteed a good implementation. In other words, the compiler does not bother whether you have code inside your method or not. All it cares is if you have methods of the matching names as in the interface. That's all… Implementation classes must adhere to the same rules for method implementation as a class extending an abstract class. In order to be a legal implementation class, a nonabstract implementation class must do the following: • Provide concrete (nonabstract) implementations for all methods from the declared interface. • Follow all the rules for legal overrides. • Declare no checked exceptions on implementation methods other than those declared by the interface method, or subclasses of those declared by the interface method. • Maintain the signature of the interface method, and maintain the same return type (or a subtype). • It does not have to declare the exceptions declared in the interface method declaration
When you implement an interface method it should be declared as public in java?
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.
What is a tagging interface type?
A tagging interface type in Java is an interface that has not defined methods such as the java.io.Serializable interface.
When would you use interface in java?
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)
Why an interface can not have anything but constants and abstract methods?
The idea is that an interface is not a class, it is just a specification of what classes that implement it must contain.
What are adapter classes in java?
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.
What is an Interface of .Net can you please give an example?
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.
What Java interface do you implement to provide methods that are called as an XML document is processed by a SAX parser?
ContentHandler
Abstract class vs interface?
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:
What does implementation mean in java?
Implementation in java mean to accomplish some aim or to execute some order in java software platform. Your class can implement more than one interface, so the implements keyword is followed by a comma with separated list of the interfaces implemented by the class. By convention, the implements clause follows the extends clause, if there is one.
What is difference between interface and abstract in java?
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.
Why use interfaces in Java?
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) Now, you might stop me and ask, what if I implement an interface and opt not to write code for a method that I am supposed to? The answer is simple. The compiler wouldn't let you do that. You cannot successfully implement an interface without providing method implementation for all the methods declared inside the interface. This is how the java system ensures that when someone knows a certain method name in an interface and has an instance of a class that implements it, can actually call that method without fear that the method isnt implemented inside the class. Assuming an interface, Convertible, with two methods: openHood(), and setOpenHoodFactor(), the following class will compile: public class Ball implements Convertible { // Keyword 'implements' public void openHood() { } public void setOpenHoodFactor(int bf) { } } Ok, I know what you are thinking now. "This has got to be the worst implementation class that you have seen". Though it compiles and runs as well, it is actually doing nothing… the interface contract guarantees that the class implementing it will have a method of a particular name but it never guaranteed a good implementation. In other words, the compiler does not bother whether you have code inside your method or not. All it cares is if you have methods of the matching names as in the interface. That's all… Implementation classes must adhere to the same rules for method implementation as a class extending an abstract class. In order to be a legal implementation class, a nonabstract implementation class must do the following: • Provide concrete (nonabstract) implementations for all methods from the declared interface. • Follow all the rules for legal overrides. • Declare no checked exceptions on implementation methods other than those declared by the interface method, or subclasses of those declared by the interface method. • Maintain the signature of the interface method, and maintain the same return type (or a subtype). • It does not have to declare the exceptions declared in the interface method declaration
When you implement an interface method it should be declared as public in java?
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.
What are two basic steps for event handling in java?
1.Implement the Listener interface and overrides its methods 2.Register the component with the Listener
