Question 1. What Is Abstraction In Java?
In java, Abstraction means display functionality and conceal complexity or internal information or disguise implementation details to the person is called abstraction in java.
The pleasant example in the international of abstraction is ATM system wherein we can withdraw or switch cash effortlessly however the way it takes place. We do not know. We don't know internal information or implementation details.
Question 2. How To Achieve Abstraction In Java?
There are two ways in java we are able to attain abstraction:
By the usage of summary elegance (zero to 100%).
By the usage of interface (a hundred%).
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Question three. What Is Abstract Class In Java?
When we declared any elegance with "summary" key-word is referred to as abstract elegance. In summary class we can maintain abstract method (with out frame) and non-summary approach (with frame).
summary class Demo
summary void display();//summary approach
void display()//non-summary approach
Question 4. Can We Create Instance Of Abstract Class?
No, we cannot create an instance of an abstract elegance.
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Question 5. Can We Define Abstract Class Without Abstract Method?
Yes, we will outline abstract class without summary method.
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Question 6. Can We Declare Abstract Method In Non-summary Class?
No, we cannot declare abstract method in non-abstract magnificence.
summary void show();
Above example will throw compile time mistakes.
Question 7. What Is Interface In Java?
An interface in java is a blueprint of a class that has static constants and summary method with the aid of default.
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Question eight. What Is Abstraction?
It refers back to the capability to make a category abstract in OOP.
It helps to reduce the complexity and also improves the maintainability of the device.
Question nine. What Is An Abstract Class?
These training can not be instantiated and are either partly implemented or on no account carried out.
This elegance carries one or extra abstract techniques which can be virtually technique declarations without a body.
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Question 10. When Is An Abstract Method Used?
An summary technique is declared in the parent magnificence when we want a class which includes a specific approach however however we want its implementation to be decided by means of infant magnificence.
Question eleven. Can An Interface Be Extended By Another Interface In Java?
An interface can be extended with the aid of any other interface in Java.
The code for the equal would be like as shown beneath:
// this interface extends from the Body interface:
public interface FourLegs extends Body
public void walkWithFourLegs( );
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Question 12. In Which Kind Of Situation Would An Interface Be Extended By Another Interface?
Remember that any magnificence that implements an interface need to put in force the method headings which might be declared in that interface.
If that precise interface extends from other interfaces, then the imposing class ought to additionally implement the strategies in the interfaces which can be being prolonged or derived from.
As shown in the example above, if we've got a category those implements the FourLegs interface, then that class need to outline the method headings in each the 'FourLegs' interface and the 'Body' interface.
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Question thirteen. Why We Use Interface In Java?
In java we use interface so that we will achieve completely abstraction because via abstract elegance we can not acquire full abstraction.
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Question 14. Can We Create Instance Of Interface?
No, we can't create item of each an interface and abstract elegance.
Question 15. Can We Declare Abstract Method As Static?
No, we cannot use static keyword with summary method.
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Question 16. Can We Declare Abstract Method As Final?
No, we cannot use final keyword with summary class.
Question 17. Can We Declare Abstract Method As Private?
No, we can't claim summary approach as private.
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Question 18. Can We Use Public, Protected And Default Modifiers With Abstract Method?
Yes, we are able to use public, protected and default modifiers with summary method.
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Question 19. Differentiate An Interface And An Abstract Class?
An summary elegance might also have many instance strategies which game default behavior.
On the other hand, an interface cannot implement any default behaviour.
However, it may claim special constants and instance strategies.
Whereas an interface has all the public contributors, an abstract magnificence incorporates only class participants like non-public, included and so on.
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Question 20. What Is A Marker Interface?
Marker interface is an interface with out a fields or techniques in Java.
Uses of marker interface are as follows:
We use marker interface to inform java compiler to add unique conduct to the elegance imposing it.
Java marker interface has no individuals in it.
It is carried out with the aid of classes which will get a few functionality.
For example whilst we want to keep the nation of an object then we are able to implement serializable interface.
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Question 21. What Will Happen If We Do Not Override All The Abstract Methods In Sub-elegance?
It will throw bring together-time error. We have to override all the abstract technique in sub-elegance. If you do no longer need to override all the abstract technique in sub-magnificence then you need to make your sub-magnificence as abstract magnificence.
Question 22. Can An Inner Class Be Built In An Interface?
Yes, an inner class can be constructed in an interface.
public interface xyz
static int p=0;
public static void most important(String c)
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Question 23. How To Define An Abstract Class?
A elegance containing abstract technique is called an abstract class. An Abstract magnificence can't be instantiated.
Example of Abstract magnificence:
abstract class test Abstract Class
protected String myString;
public String get String()
go back myString;
public abstract string any Abstract Function();
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Question 24. How Can We Define An Interface?
In Java an interface simply defines the methods and now not put in force them. Interface can include constants.
A magnificence that implements the interfaces is bound to put into effect all the methods described in an interface.
Example of Interface :
public interface pattern Interface
public void feature One();
public lengthy CONSTANT_ONE = one thousand;
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Question 25. How Do We Use Comparator And Comparable Interfaces?
java.Util.Comparator: compares a few other instructions times.
java.Lang.Comparable: compares another item with itself.