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Core Java - Interview Questions and Answers for 'Yes-no' - 33 question(s) found - Order By Newest

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 Q1. Can constructors be synchronized in Java ?Core Java
Ans. No. Java doesn't allow multi thread access to object constructors so synchronization is not even needed.

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   Like         Discuss         Correct / Improve     synchronization   synchronize   constructor   java   multithreading   yes-no   advanced     Asked in 1 Companies      expert        rare


 Q2. Can we use null as a key for a map collection ?Core Java
Ans. Yes , for HashMap. HashMap implements Map interface. HashMap allows one null key and any number of null values.

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 Q3. Can we declare interface methods as private ?
Ans. With Java 9 we can declare interface methods as private

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  Q4. Can we overload main method in Java ?Core Java
Ans. Yes, but the overloaded main methods without single String[] argument doesn't get any special status by the JVM. They are just another methods that needs to be called explicitly.

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   Like         Discuss         Correct / Improve     java   main method   overloading   yes-no     Asked in 6 Companies      intermediate        frequent


 Q5. Can we override static methods ? Why ?Core Java
Ans. No.

Static methods belong to the class and not the objects. They belong to the class and hence doesn't fit properly for the polymorphic behavior.

A static method is not associated with any instance of a class so the concept of overriding for runtime polymorphism using static methods is not applicable.

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   Like         Discuss         Correct / Improve     java   oops   static   static methods   java keywords   yes-no      intermediate        frequent


 Q6. Can we reduce the visibility of the inherited or overridden method ?Core Java
Ans. No.

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   Like         Discuss         Correct / Improve     java   oops   access specifier   overriding   overridding   inheritence   yes-no


 Q7. Can we have multiple servlets in a web application and How can we do that ?Java EE
Ans. Yes by making entries in web.xml

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   Like         Discuss         Correct / Improve     j2ee   servlets   servelets   web application   java   web.xml   yes-no   architecture


 Q8. Can we instantiate the object of derived class if parent constructor is protected ?Core Java
Ans. Yes, as protected constructor is accessible in sub class.

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   Like         Discuss         Correct / Improve     java   oops   constructor   access specifier   protected   yes-no  private constructor


 Q9. Can we declare an abstract method private ?
Ans. No Abstract methods can only be declared protected or public.

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 Q10. Can we call constructor explicitly ?
Ans. Yes.

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 Q11. Is it possible to compile and run a Java program without writing main( ) method?
Ans. Yes, it is possible by using a static block in the Java program.

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 Q12. Does java allow implementation of multiple interfaces having Default methods with Same name and Signature ?Core Java
Ans. No. Compilation error.

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 Q13. Can we use static method definitions in Interfaces ?Core Java
Ans. Yes, Effective Java 8.

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 Q14. Can we reduce the visibility of the overridden method ?Core Java
Ans. No

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   Like         Discuss         Correct / Improve     overriding   access specifier   oops   java   yes-no


 Q15. Does Java provides default copy constructor ?Core Java
Ans. No

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 Q16. Is runnable a Marker interface ?Core Java
Ans. No , it has run method declared.

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 Q17. Will Compiler creates a default no argument constructor if we specify only multi argument constructor ?
Ans. No, Compiler will create default constructor only if we don't specify any constructor.

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 Q18. Can we overload constructors ?
Ans. Yes.

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   Like         Discuss         Correct / Improve     java   oops   constructors   overloading   yes-no   basic interview question


 Q19. Do we need to import java.lang package ?Core Java
Ans. No, It is loaded by default by the JVM.

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 Q20. Can finally block be used without catch ?Core Java
Ans. Yes but should follow "try" block then.

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   Like         Discuss         Correct / Improve     java   exceptions   exception handling   try   catch   finally   yes-no

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 Q21. Is JVM a overhead ?
Ans. Yes and No. JVM is an extra layer that translates Byte Code into Machine Code. So Comparing to languages like C, Java provides an additional layer of translating the Source Code.

C++ Compiler - Source Code --> Machine Code
Java Compiler - Source Code --> Byte Code , JVM - Byte Code --> Machine Code

Though it looks like an overhead but this additional translation allows Java to run Apps on all platforms as JVM provides the translation to the Machine code as per the underlying Operating System.


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 Q22. Is it legal to initialize List like this ?


LinkedList l=new LinkedList();
Ans. No, Generic parameters cannot be primitives.

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 Q23. Can finally block throw an exception ?Core Java
Ans. Yes.

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 Q24. Will this code Work ? If not , Why ?

java.util.Calendar c = new java.util.Calendar();
Core Java
Ans. No. It gives the error "Cannot Instantiate the type Calendar". Calendar is an abstract class and hence Calendar object should be instantiated using Calendar.getInstance().

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   Like         Discuss         Correct / Improve     java   date   calendar   abstract class   yes-no


 Q25. Can value be null in TreeMap ?Core Java
Ans. Yes.

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 Q26. Is It Good to use Reflection in an application ? Why ?Core Java
Ans. no, It's like challenging the design of application.

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   Like         Discuss         Correct / Improve     java   reflection api   yes-no   architecture     Asked in 1 Companies      intermediate


Rarely asked as default methods have been introduced with Java 8.
 Q27. Can we have a default method without a Body ?Core Java
Ans. No. Compiler will give error.

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Rarely asked as default methods have been introduced with Java 8.
 Q28. Can we have a default method definition in the interface without specifying the keyword "default" ? Core Java
Ans. No. Compiler complains that its an abstract method and hence shouldn't have the body.

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 Q29. Can we extend an Enum ?Core Java
Ans. No. Enums are final by design.

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 Q30. Should we create system software ( e.g Operating system ) in Java ?Core Java
Ans. No, Java runs on a virtual machine called JVM and hence doesn't embed well with the underlying hardware. Though we can create a platform independent system software but that would be really slow and that's what we would never need.

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