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Core Java - Interview Questions and Answers for 'Core Java' - 1246 question(s) found - Order By Rating

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 Q1. Explain method overridding.Core Java2020-09-16 11:52:28

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 Q2. Write a program to print next largest palindrome number? Core Java2020-09-16 11:51:37

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 Q3. String processing in JavaCore Java2020-02-13 08:15:31

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 Q4. What is concurrent interface ?Core Java2020-02-07 09:48:12

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   Like         Discuss         Correct / Improve     Concurrent Interface   java.util.concurrent   Java 8 Concurrency   java concurrency   java 8     Asked in 1 Companies


 Q5. What are the benefits of Java over other Programming Languages ?Core Java2020-01-30 09:57:43

Ans. 1. JVM that makes it platform independent and facilitates portability.
2. Garbage Collector that protects from Memory Leaks.
3. Only usage of references and not pointer arithmetic and hence protects the application from memory issues like dangling pointers, memory leaks etc.
4. Support for OOPs that makes application development and maintenance easy.
5. Facilitates library development through use of interface / abstract classes.
6. Facilitates creation of scalable applications.
7. Huge repository of libraries and pool of people with java skill.

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   Like         Discuss         Correct / Improve     benefits of java  advantages of java      basic        frequent


 Q6. What is the different between collection and Stream Api ?Core Java2020-01-30 09:23:49

Ans. data under collection are actually stored in memory so that they can be retrieved when needed whereas data in streams are not stored and hence we need to construct it again when needed.

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 Q7. Interface vs AbstractionCore Java2020-01-24 09:18:00

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 Q8. How can we create an arraylist of unique values ?Core Java2020-01-17 09:28:36

Ans. We can put the value in a set to enforce uniqueness and then dum those value into an arraylist.

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 Q9. Why wait(), notify(), notifyAll() methods are in Object class instead of Thread class?Core Java2020-01-14 09:48:22

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 Q10. Can the value of a static variable be changed ? Core Java2020-01-12 23:16:52

Ans. Yes the value of a static variable can be changed. It's the final keyword that restrict the modification of value not static.


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 Q11. What are the advantages and disadvantages of Lambda Expression ?Core Java2020-01-10 15:55:43

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 Q12. Write a program to make an array act as a set.Core Java2020-01-10 15:48:48

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 Q13. What is the use of defining equals , compareTo and hashcode methods in a class ? Where are they used ?Core Java2020-01-09 16:32:57

Ans. equals, compareTo and hashcode are of use when the objects are used within collections.

Equals helps with collections that helps maintaining only unique objects ( like Set )

compare and compareTo helps with collections that helps maintaining objects in order ( TreeSet, TreeMap etc )

hascode helps with collections that facilitates hash searching ( like hashSet, hashMap etc )

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   Like         Discuss         Correct / Improve     equals    compareTo   hashcode method


 Q14. Write a Program to draw a fish ?Core Java2020-01-02 15:43:37

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 Q15. Should we do anything to avoid memory leaks in Java ?Core Java2020-01-02 09:47:12

Ans. Java has a intrinsic way of checking leaks and reclaiming memory called garbage collection. Moreover Java doesn't support pointer arithmetics , so there is very low comparative chance of memory leaks, compared to C,C++

Though there may be tools that may audit code to make sure that we are not leaving much for the garbage collection to work but I have never heard anyone doing anything for memory leaks in Java.

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 Q16. Explain Collections in JavaCore Java2019-12-30 18:34:31

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 Q17. Is String mutable or immutable in Java ?Core Java2019-12-30 18:32:28

Ans. String is Immutable because of String Constant Pool.

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 Q18. What are different types of Polymorphism in Java ?Core Java2019-12-30 18:31:52

Ans. run time polymorphism
compile time polymorphism

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 Q19. Can we assign the reference to this variable ?Core Java2019-12-23 18:14:55

Ans. No

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 Q20. Hash map using/without using Java 8Core Java2019-12-17 12:35:15

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 Q21. What is Throwable ?Core Java2019-12-11 14:29:13

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 Q22. What is string pool and what is the use of intern() function ?Core Java2019-11-22 12:22:44

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 Q23. How to make a collection thread safe?Core Java2019-11-21 14:50:50

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 Q24. What is a comparator ?Core Java2019-11-18 14:01:29

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 Q25. Why should we go for custom defined exceptions even if we have many exceptions provided already using throw keywordCore Java2019-11-14 16:16:09

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 Q26. How does Garbage Collector work? What are the realizations of Garbage Collector.Core Java2019-10-28 15:24:28

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 Q27. How multiple catch block works ?Core Java2019-10-27 12:33:22

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 Q28. What is the use of toString method ?Core Java2019-10-14 11:15:09

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 Q29. Class and Object methods.Core Java2019-09-30 08:24:05

Ans. class:- A class describe the contents of an object, an it describe the detail of data field called instance variable and defines the operations called method.

Object:-An object is an element of a class. Object have the behaviors of their class.

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 Q30. How to get collections from a StreamCore Java2019-09-30 08:23:20

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