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Ans. Keep it as a Abstract Class if its a "Is a" Relationsship and should do subset/all of the functionality. Keep it as Interface if its a "Should Do" relationship.
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Q76. Difference between new operator and Class.forName().newInstance() ?
Ans. new operator is used to statically create an instance of object. newInstance() is used to create an object dynamically ( like if the class name needs to be picked from configuration file ). If you know what class needs to be initialized , new is the optimized way of instantiating Class.
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Ans. 1. It shouldn't result in infinite loop. Please make sure that you have a condition that will terminate the loop and that condition should be reached.
2. Make sure to use the break statement if you aspire to only look for something. Not using break will unnecessarily execute it till the end of for loop in some cases.
3. Similarly use continue to execute the loop with next iteration and bypass the rest of the code block if required.
4. Try to avoid multiple nesting of for loops. If it''s required, Make sure to use break and continue properly so as to avoid some unnecessary processing.
5. Make sure to use try catch within the loop and not outside the for loop if you expect it to continue if one of the iteration fails.
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LikeDiscussCorrect / Improve java loops continue break for loop control statements loop statement.while loop control statements loop statement architecture
Q79. Which of the following cannot be marked static ?
a. Constructors , Classes ( Outer ) , Classes ( nested ), Interfaces , Local variables , Inner Class methods and instance variables. b. Constructors , Classes ( Outer ) , Interfaces , Local variables , Class variables , Class Methods , Inner Class methods and instance variables. c. Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables. d. Constructors , Classes ( Outer ) , Classes (Nested), Interfaces , Local variables , Inner Class methods and instance variables
Ans. Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables.
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Methods , Variables , Initialization Blocks and Outer Classes and nested Classes.
Methods , Variables , Initialization Blocks and Outer Classes.
Methods , Variables , Initialization Blocks and nested Classes.
Which of the following cannot be marked static ?
Constructors , Classes ( Outer ) , Classes ( nested ), Interfaces , Local variables , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Interfaces , Local variables , Class variables , Class Methods , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Interfaces , Local variables , Inner Class methods and instance variables.
Constructors , Classes ( Outer ) , Classes (Nested), Interfaces , Local variables , Inner Class methods and instance variables.
Q80. Interface can only have ...
a. Member elements and Methods. b. Static Variables and Static Methods. c. Static Final Variables and Instance Method Declarations. d. Member Elements , Instance Methods, Static variables and Static Methods.
Ans. Static Final Variables and Instance Method Declarations.
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Ans. Yes, we can do that. Compiler wont complain. But using object reference we can only access methods which have been defined for object class i.e clone(), equals(), hashCode(), toString() etc.
We cannot access methods defined in String class or in any class in hierarchy between String and Object.
For example - we cannot do obj.append("abc") as it will now give compile time error.
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2. for Each loop syntax is more clean if we have to iterate over the elements of a collection and we need not keep track of the record count
3. For is preferred when we need loops without the usage of collections or Array of objects and entirely primitives are being used
4. for loop is preferred if we need to keep track of record count and have to perform some action of the basis of that. For example - If we have to print something after every 5 records, With for each loop in such case, we will have to keep a separate counter.
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Q83. How does java identifies which method to be called in method overriding or runtime polymorphism, when both methods share the same name and signature ?
Ans. Encapsulation facilitate hiding and restricted access and hence more of a security feature. Encapsulation is definitely a great feature as when applications expand criss cross communication between objects / modules could lead to blunders.
Inheritance facilitates code reuse.
Polymorphism comprise of method overloaded ( which to me is negligible usage ) and method overriding. Method overriding is of great usage as it facilitates concept of interfaces and plugin development.
So it’s Security / Organization vs
Code Reuse / Support for other features like overriding vs
Contracts / Plugin Development facilitating the creation of frameworks / libraries.
Which is more important may vary from application to application , its scale , its use , its sensitivity etc.
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Ans. Yes, to a certain extent. But the objective for Final class could be beyond just enforcing composition as certain classes might have been created without inheritance or composition in mind.
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Ans. 1. Enforcing composition over inheritance
2. Restricting overriding of certain methods
3. Final methods are faster than regular instance methods
4. Enforcing Immutability
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LikeDiscussCorrect / Improve final class reasons for final class restricting inheritance object oriented programming (oops) oops concepts expert
Q89. What is cyclic instantiation ? Have you ever faced any problem due to this ?
Ans. Cyclic instantiation in OOPs may happen if Class A loading results in Class B Loading , and then Class B Loading results in Class C loading and then Class C has a static reference to Class A and hence results in cyclic instantiation or loading.
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Ans. What if the initialization throws an exception. In that case , it will let it move forward without initializing the final field. So it's a way to enforce that either the field is initialized or it fails completely.
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