This question already has answers here:
Is there more to an interface than having the correct methods
(17 answers)
Closed 8 years ago.
why interface is introduced in java? The abstract class only do the job of interface then, what is use of interface ?
Abstract class can have common methods and abstract methods so that if class need to implement methods which interface forced to imppliments ,instead class can extend abstract class which also forced to implement methods like interface and child class can get inherits methods of abstract class which interface dosent have this facilty .
Advantage: by using interface concept we can achieve multiple inheritance means one class can implement more than one interfaces.
Related
This question already has answers here:
Why is there no universal base class in Swift?
(2 answers)
Closed 5 years ago.
The Apple's developer documentation says:
NSObject is
The root class of most Objective-C class hierarchies, from which subclasses inherit a basic interface to the runtime system.
I wonder what is the root class of all classes in Swift in the example below:
class MyClass {
....
}
Swift classes do not inherit from a universal base class. Classes you
define without specifying a superclass automatically become base
classes for you to build upon.
https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Inheritance.html
Is that what you were looking for? :)
This question already has answers here:
Difference between static function and singleton class in swift [closed]
(3 answers)
Closed 6 years ago.
I have made a class that will contain all the utility methods. So, instead of making it as a singleton, I have marked the methods as static and accessing those methods by the ClassName.methodName without the need for instantiation.
Is this approach OK?
Just consider that a singleton is used in order to ensure that only one instance exists for a given class, and that there’s a global access point to that instance.
I believe that having all utility functions marked as static within a class is a good approach since, as you have stated, you will need to use ClassName.methodName in order to use them.
In addition, based on what you want to achieve and the information provided by this link, I would reassert that having a class with static methods is the best alternative.
how can a class or interface can extend more than one class in java Please help..
Steps:::javap java.time.chrono.ChronoLocalDateTime in cmd prompt
Compiled from "ChronoLocalDateTime.java"
public interface java.time.chrono.ChronoLocalDateTime<D extends java.time.chrono.ChronoLocalDate> ex
tends java.time.temporal.Temporal, java.time.temporal.TemporalAdjuster,
Excepting Object, which has no superclass, every class has one and only one direct superclass (single inheritance). In the absence of any other explicit superclass, every class is implicitly a subclass of Object.
if you need multiherence you need implements interfaces
look this
https://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html
This question already has answers here:
What is the rationale behind having companion objects in Scala?
(7 answers)
Closed 7 years ago.
As we know we don't have static methods in scala. If we have to achieve that taste we declare that class as object. But the problem is that when we declare class as object then all methods present in that object becomes static. And in class all methods all non-static. What I want is that to have static as well as non static methods in the same class, Is it possible? Definitely it would be possible but how??????
To do what you are trying do in Scala you create an object and a class of same name. Put static in object and instance members in Class version of it. This object is called a companion object.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Use of Java [Interfaces / Abstract classes]
Why we use interface and abtract class and in which situation one should use abstract class and interface ?? can anyone explain this with simplest example .....
You want to use an Interface when you want all your sub-types to implement different specific logic, like in this case:
interface GeometricalShape{
# only abstract methods are allowed
GetArea();
GetPerimeter();
}
In this case each geometric shape will have to implement specific logic to calculate Area and Permimeter.
You want to use an Abstract Class when although your sub-types have to implement some specific logic, you still have logic common to all sub-types like in this case:
abstract class GeometricalShape{
name;edgeCount;
protected GeometricalShape(name,edgeCount)
#abstract methods
abstract GetArea();
abstract GetPerimeter();
#Concrete methods
GetName(){return name;}
GetEdgesCount(){return edgesCount}
In this example each geometric shape will have to implement specific logic regarding Area and Perimeter like before, but now all sub-types will share common methods for retrieving the name and edge count of the geometrical, which would be redundant to be defined in each and every sub-class.