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Interview Questions and Answers for 'Java' - 1662 question(s) found - Order By Rating

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 Q1. What is Array.Map function ? What will be output of following ?

const myArray = [1, 4, 9, 16];
const result = myArray.map(x => x * 2);
Javascript
Ans. It will create an array with each value as x*2

[2, 8, 18, 32]

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 Q2. Why cannot we initialize a final field within the constructor if the initialization is within try block ?Core Java
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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   Like         Discuss         Correct / Improve     oops


 Q3. Can we initialize final fields within the constructor ? Why ?Core Java
Ans. Yes, Because final fields needs to be initialized before the construction of the object completes. Not necessarily at the time of class loading.

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 Q4. Is it safe to use session storage ?Javascript
Ans. Session storage can be accessed from XSS (Cross site Scripting) attacks but cookies (if set with "HttpOnly" and "Secure" flags) are more safer against these attacks.

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   Like         Discuss         Correct / Improve     session storage  security


 Q5. How can you trim all strings in an array ?
Ans. array.map(s => s.trim())

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 Q6. What are the main features of Java?Core Java
Ans. a) Object Oriented
b) Simple
c) Platform Independent
d) Secured
e) Robust
f) Portable
g) Multithreaded
h) Distributed

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 Q7. What are the fundamental principles of object oriented programming? / What are the OOPs concepts?Core Java
Ans. a) Inheritance
b) Abstraction
c) Polymorphism
d) Encapsulation

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 Q8. What do you mean by inheritance in java?Core Java
Ans. Inheritance is one of the key principle of object oriented programming. Through inheritance, one class can inherit the properties of another class. The class from which properties are inherited is called super class and the class to which properties are inherited is called sub class.

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 Q9. How can print the whole object state in the console in javascript ?Javascript
Ans. We can JSON.stringify

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 Q10. What are the differences between static and non-static methods?Core Java
Ans. Static method is common to all instances of a class. Static methods are stored in the class memory. Whereas non-static methods are stored in the object memory. Each instance of a class will have their own copy of non-static methods.

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 Q11. What are the different ways of creating threads in java?Core Java
Ans. There are two ways to create the threads in java
a) By extending java.lang.Thread class.
b) By implementing java.lang.Runnable interface.

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 Q12. What are Loops in Java? What are three types of loops?Core Java
Ans. Looping is used in programming to execute a statement or a block of statement repeatedly. There are three types of loops in Java:
1) For Loops
For loops are used in java to execute statements repeatedly for a given number of times. For loops are used when number of times to execute the statements is known to programmer.
2) While Loops
While loop is used when certain statements need to be executed repeatedly until a condition is fulfilled. In while loops, condition is checked first before execution of statements.
3) Do While Loops
Do While Loop is same as While loop with only difference that condition is checked after execution of block of statements. Hence in case of do while loop, statements are executed at least once.

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 Q13. What is the difference between double and float variables in Java?Core Java
Ans. In java, float takes 4 bytes in memory while Double takes 8 bytes in memory. Float is single precision floating point decimal number while Double is double precision decimal number.

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 Q14. Can main() method in Java can return any data?Core Java
Ans. In java, main() method can't return any data and hence, it's always declared with a void return type.

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 Q15. What's the difference between an array and Vector?Core Java
Ans. An array groups data of same primitive type and is static in nature while vectors are dynamic in nature and can hold data of different data types.

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 Q16. How to swap two numbers without using a third variable?Core Java
Ans. int a = 10;
int b = 20;

b = b + a; // now b is sum of both the numbers
a = b - a; // b - a = (b + a) - a = b (a is swapped)
b = b - a; // (b + a) - b = a (b is swapped)

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 Q17. Explain method overridding.Core Java
 This question was recently asked at 'Ksolves'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     overridding  polymorphism     Asked in 1 Companies


 Q18. Write a program to print next largest palindrome number? Core Java
 This question was recently asked at 'Ksolves'.This question is still unanswered. Can you please provide an answer.


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 Q19. What are the benefits of using UI framework like Angular , View js etc instead of plain vanilla js and html ?Javascript
Ans. These frameworks facilitates easier product development and enhancement and maintainability by having separation of concerns ( using oops ) and helps in development of reusable libraries / components. So in nutshell , they make development and maintenance of large scale application easier.

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   Like         Discuss         Correct / Improve     Javascript Frameworks  Angular  View js


 Q20. Have you ever used sessionStorage ? What is the better way to store session information - sessionStorage or session cookie ?Session Management
Ans. Session Cookie, because session storage can be accessed from XSS (Cross site Scripting) attacks but cookies (if set with "HttpOnly" and "Secure" flags) are more safer against these attacks.

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   Like         Discuss         Correct / Improve     SessionStorage  session cookie  session management  javascript


 Q21. String processing in JavaCore Java
 This question was recently asked at 'Chase'.This question is still unanswered. Can you please provide an answer.


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 Q22. what is strict mode in javascript ? How is it used ?Javascript
 This question is still unanswered. Can you please provide an answer.


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 Q23. What is concurrent interface ?Core Java
Ans. ConcurrentMap is an interface and it is a member of the Java Collections Framework. It represents a Map that is capable of handling concurrent access to it without affecting the consistency of entries in a map. ConcurrentMap interface present in java.util.concurrent package.

HashMap operations are not synchronized, while Hashtable provides synchronization. Though Hashtable is thread-safe, it is not very efficient. To solve this issue, the Java Collections Framework introduced ConcurrentMap in Java 1.5.

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


 Q24. What are the benefits of Java over other Programming Languages ?Core Java
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


 Q25. What is the different between collection and Stream Api ?Core Java
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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 Q26. How is cohesion achieved in JavaScript ?JavaScript
 This question is still unanswered. Can you please provide an answer.


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 Q27. How Object-Oriented Programming is implemented in JavaScript? How they differ from other languages?Javascript
 This question is still unanswered. Can you please provide an answer.


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 Q28. Explain Servlet configJava EE
 This question was recently asked at 'Oracle financial services'.This question is still unanswered. Can you please provide an answer.


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 Q29. Interface vs AbstractionCore Java
 This question was recently asked at 'Oracle financial services'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     interface vs abstraction  interfacing vs abstraction  relation between interface and abstraction  How interface provide abstraction     Asked in 1 Companies


 Q30. How is the declaration of enum in Typescript differ from Javascript ?TypeScript
 This question is still unanswered. Can you please provide an answer.


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