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Which abstract class is the super class of all classes used for writing characters?
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∙ 14y ago
java.io.Writer
Wiki User
∙ 14y ago
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What is true about true about abstract data type Object of an abstract class type cant be created. We can derive classes from these abstract classes Object of an abstract class t?
True - an instance of an abstract class cannot be created. False - derive (subclass) from a class, not the object (the instance).
What can be declared in an abstract class?
Abstract classes are to be extended until to a concrete class.Can have both abstract & non abstract methods.An Abstract class can not be instantiated.A non abstract class can be extended to an abstract class.If At least one abstract method present in a class then that class must be abstract.abstract & final modifiers can never be together.abstract classes can have both abstract methods & non abstract methods.
How do you call an abstract class from main method?
An abstract class cannot have a constructor and hence you cannot invoke the constructor of the class - i.e., you can instantiate an abstract class and hence you cannot call the constructor of an abstract class.
What is the difference between abstract class and normal class?
Any class which has one or more abstract methods is called an abstract class. But in the normal class we can't have any abstract methods. We cannot create an object for the abstract classes. When we inherit the abstract class we should implement the abstract method which we inherit.
Can a class in java extend both abstract class and concrete class?
An Abstract class is similar to an interface. You cannot instantiate them, but you can extend them. Any class that extends the abstract class has to provide the implementation to the abstract methods. Hence these classes can be used as a skeleton to similar classes where some common functionality may be required. Such functionality can also be embedded into these classes. Unlike interfaces, abstract classes can have method code also. So they are very useful.
How do you write concrete method inside abstract class?
There is no difference with method declaration and implementation between abstract and non-abstract classes. You do the exact same thing when writing a concrete method in either an abstract or non-abstract class.
What is true about true about abstract data type Object of an abstract class type cant be created. We can derive classes from these abstract classes Object of an abstract class t?
True - an instance of an abstract class cannot be created. False - derive (subclass) from a class, not the object (the instance).
What can be declared in an abstract class?
Abstract classes are to be extended until to a concrete class.Can have both abstract & non abstract methods.An Abstract class can not be instantiated.A non abstract class can be extended to an abstract class.If At least one abstract method present in a class then that class must be abstract.abstract & final modifiers can never be together.abstract classes can have both abstract methods & non abstract methods.
How do you call an abstract class from main method?
An abstract class cannot have a constructor and hence you cannot invoke the constructor of the class - i.e., you can instantiate an abstract class and hence you cannot call the constructor of an abstract class.
What is the difference between abstract class and normal class?
Any class which has one or more abstract methods is called an abstract class. But in the normal class we can't have any abstract methods. We cannot create an object for the abstract classes. When we inherit the abstract class we should implement the abstract method which we inherit.
What happens if an abstract modifier is applied to class. Explain?
The classes which have one or more abstract methods are abstract. To declare a class as abstract, use the abstract keyword in front of the class keyword, before the class declaration. Abstract classes cannot be instantiated. Similarly the new keyword cannot be used to create an object of the abstract class. Remember that the constructors and static variables cannot be declared as abstract. Any subclass of an abstract class must either implement all of the abstract methods in the superclass or be itself declared abstract.
Can a class in java extend both abstract class and concrete class?
An Abstract class is similar to an interface. You cannot instantiate them, but you can extend them. Any class that extends the abstract class has to provide the implementation to the abstract methods. Hence these classes can be used as a skeleton to similar classes where some common functionality may be required. Such functionality can also be embedded into these classes. Unlike interfaces, abstract classes can have method code also. So they are very useful.
What is the difference abstract class and interface?
They are very different. An abstract class is a class that represents an abstract concept (Google define "abstract" if you're unsure) such as 'Thoughts' or 'BankAccount'. When a class is defined as abstract it cannot be used (directly) to create an object. Abstract classes are used as super-classes so that all of their subclasses inherit all methods. Interfaces can be thought of as contracts with all of their implementing classes. They simply require all implementing classes to have methods with the same signature as that defined in the interface, but such methods can behave as appropriate. Hope that helps :)
Compare anonymous class with abstract class?
Abstract Classes contain the work abstract in it. It is used when you know that you will need to use an object of its type but do not know the inner workings yet. Anonymous classes are those classes that are constructed on the fly. You need to know its inner workings.
Is an abstract class cannot have any member variable in C plus plus?
An abstract base class may have member variables. Whether or not it actually needs member variables depends on the nature of the base class itself. If the variable is common to all derived classes, then it makes sense to place the variable in the base class. If some derived classes have no need of the variable, then it is better to derive an intermediate class with the variable, and to derive those classes that require that variable from the intermediate class, rather than directly from the abstract class.
What are the class loaders in Java?
A class loader is an object that is responsible for loading classes. The class ClassLoader is an abstract class.
Why you are not allowed to put an abstract method into a normal class?
You can't put an abstract method (pure-virtual method) in a normal class because the normal class would become abstract itself. Only non-abstract classes can be physically instantiated as objects, and only if they fully implement all the abstract methods inherited from their base classes.
