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In java why method defined in super class need not to defined in subclass?
Wiki User
∙ 14y ago
In Java, or in any object oriented language such as C++, a method defined in super (parent) class does not need to be defined in a subclass, because that is the primary purpose of inheritance.
Object oriented programming allows you to define and declare a class that implements the behavior for an object. Inheritance allows you to refine, or subclass, that class by "reusing" all of the functionality of the parent class into the sub class, adding additional definition and declaration for the sub class.
If the subclass needs to change a parent class method, it can overload that method. This is called abstraction.
Wiki User
∙ 14y ago
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Can you call an abstract method from a non abstract method in java?
We can't call (i.e, execute) an abstract method in java because these methods don't contain any code to execute!In some special cases like when an abstract method is overridden in a subclass, and when we are using super class reference variable( which is referring that subclass object), it appears that we are calling abstract method in super class. But actually the code in the subclass method is being executed.Example:abstract class SuperClass{abstract void show(); //abstract method in super class}class SubClass extends SuperClass{void show(){ //show() of SuperClass overridden in SubClassSystem.out.println("SubClass Method");}}class Example{public static void main(String... args){SuperClass sup=new SubClass();sup.show(); //SubClass show() will be executed !!!}}
It is an error to have a method with the same signature in both the super class and its subclass. True or false?
False. A method with the same signature in both the superclass and its subclass is known as method overriding, and is a valid concept in Java.
Any method in a super class can be overridden in its subclass?
False.Any method declared as final cannot be overridden by any subclasses.You also cannot technically override a private method. While your subclass can have a method with the same definition as a private method in the superclass, it does not actually override that method.
How super class variable can be used to refer the sub class object?
The super variable is not a reference to a subclass. It is a reference to the superclass. class MyClass { void printType() { System.out.println("This is a MyClass"); } // MySubClass is a subclass of MyClass. Within this class, the super keyword // refers to MyClass. static class MySubClass extends MyClass { void printType() { // Tell Java we also want to call the printType method of the super class super.printType(); System.out.println("This is a MySubClass"); } } }
What portions of a super class can be used by subclass?
Any members of a superclass which are declared as public or protected can be used by all subclasses.
A subclass can call constructor method defined by its super class?
True
S it an error to have a method with the same signature in both the super class and its subclass?
No; you may decide to change the behaviour of a method in the subclass, or to add additional functionality.
Can you call an abstract method from a non abstract method in java?
We can't call (i.e, execute) an abstract method in java because these methods don't contain any code to execute!In some special cases like when an abstract method is overridden in a subclass, and when we are using super class reference variable( which is referring that subclass object), it appears that we are calling abstract method in super class. But actually the code in the subclass method is being executed.Example:abstract class SuperClass{abstract void show(); //abstract method in super class}class SubClass extends SuperClass{void show(){ //show() of SuperClass overridden in SubClassSystem.out.println("SubClass Method");}}class Example{public static void main(String... args){SuperClass sup=new SubClass();sup.show(); //SubClass show() will be executed !!!}}
It is an error to have a method with the same signature in both the super class and its subclass. True or false?
False. A method with the same signature in both the superclass and its subclass is known as method overriding, and is a valid concept in Java.
Any method in a super class can be overridden in its subclass?
False.Any method declared as final cannot be overridden by any subclasses.You also cannot technically override a private method. While your subclass can have a method with the same definition as a private method in the superclass, it does not actually override that method.
How super class variable can be used to refer the sub class object?
The super variable is not a reference to a subclass. It is a reference to the superclass. class MyClass { void printType() { System.out.println("This is a MyClass"); } // MySubClass is a subclass of MyClass. Within this class, the super keyword // refers to MyClass. static class MySubClass extends MyClass { void printType() { // Tell Java we also want to call the printType method of the super class super.printType(); System.out.println("This is a MySubClass"); } } }
What do you meant by Runtime Polymorphism?
Runtime polymorphism is also called as method overriding, late binding or dynamic polymorphism. It is when a method in a subclass overrides a method in its super class with the same name and signature.
How do explicitly invoke overridden superclass method from a subclass?
Use the super keyword. Example: public class Super { public void methodToOverride() { } } public class Sub { @Override public void methodToOverride() { super.methodToOverride(); } }
What portions of a super class can be used by subclass?
Any members of a superclass which are declared as public or protected can be used by all subclasses.
Can a super class varialble can reference a subclass object in java?
No. Because, what is the guarantee that when the super class code is being executed there will always be a sub class? But, the other way round - sub class object accessing a super class variable is possible because, if a sub class uses inheritance to extend from another class, then it is 100% sure that the parent class is going to be around. So a sub class can access the super class variable.
What you call those subclass having more than one super-class?
category
What you call those subclass having more than one super class?
category
