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What else can I help you with?
Why instance in abstract or interface?
we can make object of interface but in abstract we can not make object of it interface ab= new Classs(): in interface we maintain multiple inhetence by use of obj of interface we if inherit two class have same fun then we give the name of that interface and call the pertucular that fun interface ab= new class() ab.add(); but in Astract Class we cannot make object of it only class class wich inherit it can make object class ab2= new Class(); and by obj we call function of drived class ob2.add();
What is abstaction in java?
The concept of abstraction is concept talked about when talking about inheritance. When you make a class abstract, it means that the class is a general "abstract" idea, not something you want to instantiate (create an object from.) However, abstract classes are useful for when you want to create real sub-classes of the abstract class. For example, you could have an abstract class named "animal" that had the general characteristics of all animals, then you can have regular sub-classes that inherit "animal", like "dog", "cat" or "horse." The reason for making the "animal" class abstract is to make sure that one can't create a generic "animal" object, but so they can create objects that inherit the idea of "animal."
Why can't declare construtor as a static final abstract?
Because of the following reasons:static - If a constructor is static, an object instance cannot invoke it to initialize itself (Because static members are not linked to an object)abstract - because an abstract class cannot be instantiated and hence it will not have a constructor. If you make a concrete class's constructor abstract - it cannot be instantiated. eitherways it makes no sensefinal - a constructor cannot be final (thats the way java is designed)
What is abstract base class?
An abstract class is a class that cannot be directly instantiated. The purpose of such a class is to put some logic in a base class and force derived classes to implement the remaining functionality. Since the full functionality is only available in the derived class, the base class is declared as abstract so that it cannot be instantiated directly.
What are the differences between class and abstract class?
Below is the main difference between the 3 components:Concrete class - Provides implementation for all its methods & also for methods from extended abstract classes or implemented interfacesAbstract class - Does not provide implementation for one or more of its methodsInterface - Does not provide implementation for any of its methods
What abstract noun can you make from kind?
The the noun 'kind' is an abstract noun as a word for type or class; having similar characteristics.The abstract noun for kind is kindness.
Write a Java Program to illustarte the use of abstract methods?
Abstract MethodsAn abstract method is a method that's been declared as abstract but not implemented. In other words, the method contains no code. You mark a method abstract when you want to force subclasses to provide the implementation. (remember the reason why you would want to make a class abstract from the previous paragraph)Ex: public abstract void showSample();Notice that the abstract method ends with a semicolon instead of curly braces. It is illegal to have even a single abstract method in a class that is not explicitly declared abstract! Look at the following illegal class:public class IllegalAbstractClass{public abstract void test();}The preceding class will produce the following error if you try to compile it:IllegalClass.java:1: class IllegalAbstractClass must be declaredabstract.It does not define void test() from class IllegalAbstractClass.public class IllegalAbstractClass {1 errorYou can, however, have an abstract class with no abstract methods. The following example will compile fine:public abstract class LegalAbstractClass{void test() {// you can write lots of code here}}In the preceding example, test() is not abstract. Three different clues tell you it's not an abstract method:• The method is not marked abstract.• The method declaration includes curly braces, as opposed to ending in a semicolon. In other words, the method has a method body.• The method contains actual implementation code.Any class that extends an abstract class must implement all abstract methods of the superclass, unless the subclass is also abstract. The rule is this:The first concrete subclass of an abstract class must implement all abstract methods of the superclass.Concrete just means nonabstract, so if you have an abstract class extending another abstract class, the abstract subclass doesn't need to provide implementations for the inherited abstract methods. Sooner or later, though, somebody's going to make a nonabstract subclass (in other words, a class that can be instantiated), and that subclass will have to implement all the abstract methods from up the inheritance tree.
What is purpose of abstraction in java?
Abstract keyword used for method declaration declares the methods without implementations. Abstract class in java have abstract methods that is not implemented in abstract class, but implemented in subclasses in java program. If the class in java program is not required to get instantiated than that class use the abstract keyword but this class rather is available for other classes to extend by other classes. Abstract keyword will be used in method declaration to declare that method without providing the implementation in that java program. In other words we can say that, it formally unfinished class as well as method, that marked with the help of keyword abstract. Defining abstract is a way of preventing someone from instantiating a class that is supposed to be extended first. In java program abstract class is deliberately missing similar to like an interface which will missing all method bodies in the program. Abstract class provides a way to extend an actual class. We will not use new on abstract classes but will use abstract references in the java program, that always point to objects of the class that extends an abstract class. In java program for practical use of an abstract class, we will define a non-abstract class that extends an abstract one. This will use any of the inherited non-abstract methods. Most of the time abstract class may extend another abstract class. In that condition it need not implement all in the non-abstract methods. An abstract keyword used both on classes and methods. In case of class declared with an abstract keyword may not be instantiated that is the only thing that abstract keyword doing.
What is the difference between an interface and an abstract class?
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.
How can you use abstract classes instead of interfaces?
In most cases, you will want to use abstract classes IN ADDITION to interfaces.You should use an abstract class in the following circumstance:the abstract class is clearly part of class hierarchy, and does not just describe some sort of basic functionality. Specifically, abstract classes are a good idea where they will be directly inherited from to create a concrete concept, but the abstract class itself is too indistinct to have any specific instance of it created.You want to provide an implementation for a set of methods that will be reused by a significant number of other classes, all of which can be fit into a class hierarchy.In practice, abstract classes are a good way to collect common code into one place, to make maintenance easier.For instance, say you have a class and interface structure like this:Class AInterface XClass B extends A implements XClass C extends A implements XBoth B and C will have the all the methods declared in X; if the implementation of those methods is the same (or can be made the same), then X is a good candidate for changing to an abstract method:Class AAbstract Class X extends AClass B extends XClass C extends XThus, you have removed the code duplication that was happening when using interfaces.Note that doing the above is NOT a good idea if any class which implement interface X cannot be made a subclass of the new abstract class X.
What is purpose of keyword new?
The keyword new is used to instantiate or create Java class objects. ex: String empName = new String("Rocky"); The above statement creates a new String object of name empName and value as Rocky
Explain the meaning of abstract keyword in relation to classes and methods?
The abstract keyword is used to denote abstract classes and abstract methods in Java.An abstract method is a method which is defined, but not implemented:public abstract void doStuff();An abstract class is a class which contains one or more abstract methods*, and which cannot be instantiated directly. All subclasses of an abstract class must implement the abstract methods.* Note that abstract classes can include no abstract methods, but this rather defeats the purpose of using an abstract class.The quintessential example of an abstract class is the Shape class.// Definition of our abstract classpublic abstract class Shape {// Notice how we can actually declare and implement variables and methods.// This is what differentiates between an abstract class and an interface.// The location of this shapeprivate double x,y;// Change our location - all subclasses will have this by defaultpublic void moveTo(final double newX, final double newY) {x = newX;y = newY;}// Definitions of our abstract classes.// All classes which extend from Shape must implement these.public abstract double getArea();public abstract double getPerimiter();}// Definition of our concrete example classpublic class Rectangle extends Shape {// Beyond the x,y location of Shape, Rectangle must have width and heightprivate double width, height;// Implement abstract methodspublic double getArea() {return width * height;}public double getPerimiter() {return width + width + height + height;}}
