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Ans. Java provides its own implementations of the thread pool pattern, through objects called executors. These can be used through executor interfaces or directly through thread pool implementations which does allow for finer-grained control. The java.util.concurrent package contains the following interfaces:

Executor : a simple interface for executing tasks.ExecutorService a more complex interface which contains additional methods for managing the tasks and the executor itself.

ScheduledExecutorService: extends ExecutorService with methods for scheduling the execution of a task.Alongside these interfaces, the package also provides the Executors helper class for obtaining executor instances, as well as implementations for these interfaces.

Generally, a Java thread pool is composed of:

The pool of worker threads, responsible for managing the threads.
A thread factory that is responsible for creating new threads.
A queue of tasks waiting to be executed.

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Q39. Can we use try within catch block ?

Ans. Yes

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Q40. suppose i have interface and i have declare lots of abstract method in interface But in sub class only two methods are use .than how to use oly two methods.

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Q41. What is TypeCasting ?

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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Q42. Difference between Arrays and ArrayList ?

Ans. Both Arrays and ArrayLists are used to store elements. Elements can be either primitives or objects in case of Arrays, but only objects can be stored in Arraylist. Array is a fixed length data structure while arraylist is variable length collection class. Once created, you cannot change the size of the arrays, but arraylists can dynamically resize itself when needed.Another notable difference between Arrays and Arrayslist is that arary is part of core java programming and array list is part of collection classes

Sample Code for arrays arraylist

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Q43. What sets you apart from other developers ?

or

What are the distinguished qualities you have ?

Ans. https://blog.timesunion.com/careers/the-10-most-important-personality-traits-for-career-success/633/

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Q44. Explain OAuth.

Authentication

Ans. OAuth is an open-standard authorization protocol or framework that describes how unrelated servers and services can safely allow authenticated access to their assets without actually sharing the initial, related, single logon credential. Like using Google or Facebook to login to something.

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Q45. What are the types of authentication used in Web services ?

Web Service

Ans. Encrypted User Name / Password
Encrypted Password within Cookie
Encrypted Tokens
IP
Client Certificates
Oauth

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Q46. What is OSGI ?

OSGI

Ans. OSGI is open service gateway initiative, its used as java framework for developing and deploying the modular softwares.

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Q47. Have you worked on Linux Systems ?

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Q48. Describe structure of a Web application.

architecture

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Q49. Can we have multiple inheritance in java using abstract class ?

Ans. https://www.geeksforgeeks.org/arrays-sort-in-java-with-examples/

Ans. No

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Q50. Difference between == and === ?

JavaScript

Ans. == compares values === is used in scripting languages for comparing two values as well as there data tpe. like in js,php.

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Q51. Write code to sort an array.

Algorithm

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Q52. What is the difference between TreeSet and TreeMap ?

Ans. TreeSet contains only values as elements whereas TreeMap contains Key value pairs.

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Q53. What is setter injection ?

Spring

Ans. Setter Injection in Spring is a type of dependency injection in which the framework injects the dependent objects into the client using a setter method.

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Q54. What development process / methodology are you using ? Are you using agile ?

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Q55. Why do want to leave your current job ?

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Q56. How can we make sue that only 1 object gets created ?

Ans. We can use Singleton Design Pattern.

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Q57. Why did you chose programming as your career ?

Ans. I was always fascinated by mathematics and statistics and hence chose programming as I found It to be fit ground for utilizing those skills.

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Q58. What is difference between url based and component based web application ?

J2EE

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Q59. What is the use of @Import and @ImportResource anotations ?

Ans. The @Import annotation is used to import one or more @Configuration classes. This annotation provides the functionality equivalent to element in xml based configuration.

The @ImportResource annotation is used to import one or more XML configuration files.

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Q60. Write code to redo and undo without using system functions ?