Interview Questions and Answers for 'Cla' | Search Interview Question

Interview Questions and Answers for 'Cla' - 209 question(s) found - Order By Rating

Q1. What is the different between collection and Stream Api ?

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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Q2. How you debug and troubleshoot slowness with a REST call?

Rest

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Q3. When you build an angular application, what type of file it creates which we can deploy?

Angular JS

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Q4. What would you do if your rest services aren't responding fast enough ?

Rest

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Q5. What kind of deployable is created for the angular project ?

Angular Js

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Q6. What is life cycle of cloud deployment process ?

Cloud Computing

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Q7. What is JUnitRunner ?

JUnit

Ans. A JUnit Runner is a class that extends JUnit’s abstract Runner class and it is responsible for running JUnit tests.

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Q8. Difference between HashMap and Dictionary in Java ?

Core Java

Ans. HashMap implements the Map interface while the Dictionary does not.

HashMap was introduced after HashTable and Dictionary.

Dictionary is currently obsolete in java.

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Q9. difference between ArrayList and array ?

Core Java

Ans. ArrayList is a variable length collection class whereas arrays are fixed length primitive structure.

We can use generics with arraylist but not with arrays.

We can store primitive data types within arrays but can't with ArrayList. In ArrayList that needs to be converted to Wrapper objects.

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Q10. Why is String a class in Java ?

Core Java

Ans. 1. Creating a class helps in specifying operations on the Strings like length , sub string , concatenation etc.

2. It acts as a Wrapper class for "Array of Characters" and hence facilitates it's usage in collections, assignment to null.

3. Immutability of String objects facilitates in reuse , security and caching.

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Q11. Does abstract class have public constructor?

Core Java

Ans. Yes, an abstract class can have a constructor in Java.

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Q12. Difference between Base Class, Derived Class , Abstract Class and Concrete Class ?

Core Java

Ans. Base Class is a relative term used to signify the Parent class in Parent - Child or Base - derived relationship.

Derived Class is a relative term used to signify the Child class in Parent - Child or Base - derived relationship.

Abstract Class is a class that is not allowed to be instantiated and hence can serve only a base class for it's usage.

Concrete Class is the class which is supposed to be instantiated and hence provide definition for all implementing interface methods and extending abstract methods.

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Q13. Can an abstract class be a derived class ?

Core Java

Ans. Yes, an abstract class can extend another class.

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Q14. What is the relationship between Base Class and Abstract Class ?

Core Java

Ans. Abstract Class is a class that's only allowed to be a Base class for it's usage. It can never be instantiated on it's own.

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Q15. Differences between class not found exception and noclassdef found error ?

Core Java

Ans. ClassNotFoundException is an exception that occurs when we try to load a class at run time using Class.forName() or loadClass() methods and mentioned classes are not found in the classpath.

NoClassDefFoundError is an error that occurs when a particular class is present at compile time, but was missing at run time.

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Q16. Why line 4 in this code gives error saying "Cannot be referenced from a static context" ?

public class OuterClass {

public static void main(String[] args){
InnerClass innerClass = new InnerClass();
}

class InnerClass {

}
}

Core Java

Ans. InnerClass is a non static inner class and hence can only be instantiated using instance of the outer class.

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Q17. What is TypeCasting ?

Core Java

Ans. Assigning a value of one type to a variable of another type is known as Type Casting.

Example :

int x = 10;
byte y = (byte)x;

In Java, type casting is classified into two types, Widening Casting(Implicit) widening-type-conversion and Narrowing Casting (Explicitly done) narrowing-type-conversion.

Widening or Automatic type converion - Automatic Type casting take place when,the two types are compatible and the target type is larger than the source type

Example :

public class Test {
public static void main(String[] args) {
int i = 100;
long l = i; //no explicit type casting required
float f = l;//no explicit type casting required
System.out.println("Int value " i);
System.out.println("Long value " l);
System.out.println("Float value " f);
}
}

Narrowing or Explicit type conversion - When you are assigning a larger type value to a variable of smaller type, then you need to perform explicit type casting.

Example :

public class Test{
public static void main(String[] args) {
double d = 100.04;
long l = (long)d; //explicit type casting required
int i = (int)l;//explicit type casting required
System.out.println("Double value " d);
System.out.println("Long value " l);
System.out.println("Int value " i);
}
}

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Q18. Does Java generate .class file for interfaces ?

Core Java

Ans. Yes

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Q19. Why Concurrent Collection Classes are fail-fast in Java ?

Core Java

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Q20. Create an event class in Java.

Core Java

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Q21. What could be the reasons for restricting inheritance using final class ?

Core Java

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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Q22. Does use of Final class enforces composition over Inheritance in Java ?

Core Java

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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Q23. Why Java has final class ?

Core Java

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Q24. Can we have interface as a replacement for utility class ?

Core Java

Ans. Yes, With Java 8 we can use Interfaces as collection of utility methods through the use of default methods.

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Q25. Can we have multiple inheritance in java using abstract class ?

Core Java

Ans. No

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Q26. Which are the thread safe / synchronized / concurrent classes in java collections ?

Core Java

Ans. Stack
Properties
Vector
BlockingQueue
ConcurrentMap
ConcurrentNavigableMap

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Q27. Explain OOps concepts.

Core Java

Ans. There are four main OOP concepts in Java. These are:

Abstraction. Abstraction means using simple things to represent complexity. We all know how to turn the TV on, but we don?t need to know how it works in order to enjoy it. In Java, abstraction means simple things like objects, classes, and variables represent more complex underlying code and data. This is important because it lets avoid repeating the same work multiple times.

Encapsulation. This is the practice of keeping fields within a class private, then providing access to them via public methods. It?s a protective barrier that keeps the data and code safe within the class itself. This way, we can re-use objects like code components or variables without allowing open access to the data system-wide.

Inheritance. This is a special feature of Object Oriented Programming in Java. It lets programmers create new classes that share some of the attributes of existing classes. This lets us build on previous work without reinventing the wheel.

Polymorphism. This Java OOP concept lets programmers use the same word to mean different things in different contexts. One form of polymorphism in Java is method overloading. That?s when different meanings are implied by the code itself. The other form is method overriding. That?s when the different meanings are implied by the values of the supplied variables. See more on this below.

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Q28. What is abstraction ?

Design

Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user.

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Q29. What is the use of Object class ?

Core Java

Ans. 1. Default definition for some of the methods , like equals, hashcode etc that gets carried to all objects even if you don't define anything. But that default definition is kind of like assigning 0 to integer, it just provide a safe state , nothing much for comparison.

2. Places where you have no idea about what object you may receive and just want to perform out of 8 basic methods of object class, something like printing their string representation ( defined by their toString method ), or equality ( using their equals method )

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Q30. What are the benefits of immutability or Immutable classes ?

Core Java

Ans. Immutable objects are thread-safe so you will not have any synchronization issues.Immutable objects are good for Map keys and Set elements, since these typically do not change once created.Immutability makes it easier to write, use and reason about the code (class invariant is established once and then unchanged)Immutability makes it easier to parallelize your program as there are no conflicts among objects.The internal state of your program will be consistent even if you have exceptions.References to immutable objects can be cached as they are not going to change.

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