1) What is the difference between static variables and instance variables?
Answer: The below is the answer for this question:
static variables are common variables who’s values will be stored in Class memory.
instance variables are object specific variables who’s values will be stored in individual object’s memory.
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2) What is the result of specifying final modifier with Classes, Variables and Methods?
Answer: The below is the answer for this question:
final modifier can be specified to Classes, Variables and Methods.
- On specifying to Classes, the Classes cannot be inherited (i.e. Child Classes cannot be created).
- On specifying to Variables, the initially assigned values to the variables cannot be changed.
- On specifying to Methods, the methods cannot be overridden in child classes.
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3) What are abstract methods?
Answer: The below is the answer for this question:
methods specified with abstract modifier are known as abstract methods.
- abstract methods won’t have method body.
- abstract methods needs to be created under abstract class.
- All the methods in an Interface are by default abstract.
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4) Can we create abstract methods inside non-abstract classes?
Answer: The below is the answer for this question:
No, we cannot create abstract methods inside non-abstract classes.
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5) What are abstract classes?
Answer: The below is the answer for this question:
The Classes that are specified with abstract non-access modifier are known as abstract classes.
abstract classes are recommended for partial implementation, as these class can have both abstract and non-abstract methods.
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6) Can an abstract class have both abstract and non-abstarct methods?
Answer: The below is the answer for this question:
Yes, abstract classes are meant for partial implementation and hence they can contain both abstract and non-abstract methods.
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7) How to implement the abstract methods of abstract classes?
Answer: The below is the answer for this question:
We have to create the child classes for the abstract classes for implementing its abstract methods.
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8) Can we create objects for abstract classes?
Answer: The below is the answer for this question:
No. Objects cannot be created for abstract classes.ax
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9) What is the parent class of all the classes in Java?
Answer: The below is the answer for this question:
Object Class is the parent class of all the classes in Java.
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10) What is the default package in Java?
Answer: The below is the answer for this question:
java.lang is the default package in Java.
- Hence we don’t have to import the classes like System or String etc., as they belong to java.lang package.
- For using the classes which are from a different package other than java.lang, we have to import those classes.
- File class in Java, doesn’t belong to java.lang package, hence we have to import this class for using it in the Java programs.
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Happy Learning 🙂
Arun Motoori ( www.QAFox.com )
