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Q471. Explain various Searching and Sorting Algorithms ?

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Q472. Is it a good practice to use Asterick(*) in import statement to load multiple packages with single import statement ?

Core Java

Ans. No, we should be lean in loading only packages which are required. Loading packages which are not being used result in memory overheads.

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Q473. What is a Servlet Filter ?

Java EE

Ans. It's an object that can intercept http request and response and hence we can take appropriate action on those requests.

There are different types of filters based on Specifications like

Authentication
Logging
Encryption
Tokenizing

etc

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Q474. Can we override wait() or notify() methods?

Core Java

Ans. wait and notify are declared final in object class and hence cannot be overridden.

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Q475. Write an algorithm / Java Program to show duplicates in an array of n elements?

Algorithm

Ans. int duplicateArray[] = { 1, 2, 2, 3, 4, 5, 6, 8, 9}
Set unique = new HashSet();
for (int i = 0; i < duplicateArray.length; i) {
if (unique.contains(duplicateArray[i])) {
System.out.println(duplicateArray[i]);
} else {
unique.add(duplicateArray[i]);
}
}

Complexity O(n) = nHashSet contains and add has O(n) = 1

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Q476. What is a binary tree ?

Algorithm

Ans. Binary tree is a tree in which each node has up to two children.Tree is a data structure composed of nodes.Each tree has a root node(not necessary in graph theory). The root node has zero or more child nodes.Each child node has zero or more child nodes, and so on.The tree cannot contain cycles.

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Q477. What is the difference between authentication and authorization ?

Authentication

Ans. Authentication is the process of verifying the identity and credentials of the user to authenticate him into the system.

whereas

Authorization is the process by which access to a segment , method or resource is determined.

Authorization is usually a step next to authentication.

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Q478. Write a multi threaded Program that will simulate transferring of money across accounts ?

Core Java

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Q479. Write a Program to print factorial of a number using recursion

Core Java

Ans. public class BuggyBread {
public static void main(String args[]) {
System.out.println(factorial(5));
}

private static int factorial(int number){
if(number == 1){
return 1;
} else {
return number * factorial(number - 1);
}
}
}

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Q480. What is a Webdriver ?

Testing

Ans. Selenium WebDriver is a tool for automating web application testing.It helps in replicating the manual tester behavior like keyboard entry, mouse events etc and then matching the output against the expected.

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Q481. How would you do an object oriented design on animals in a zoo ?

Design

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Q482. What access the variable gets if we don't provide any access specifier ?

Core Java

Ans. It gets the default access i.e package protected.

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Q483. What is Amazon S3 ?

Amazon Web Services (AWS)

Ans. Amazon Simple Storage Service or S3 is object storage with a simple web service interface to store and retrieve any amount of data from anywhere on the web.

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Q484. Do you like Native SQL Apis like JDBC or JPA / Hibernate ?

Hibernate

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Q485. How Marker interfaces works internally ?

Core Java

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Q486. Can we overload abstract methods ?

Core Java

Ans. Yes

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Q487. What are the ways in which an application can maintain config variables ?

Ans. 1. Property files
2. config xml
3. Database

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Q488. How will you design a Log4j kind of framework.

Log4j

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Q489. Difference between log4j and slf4j ?

Logging

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Q490. Difference between Virtual Memory and Demand Paging?

Operating System

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Q491. What are the advantages of using methods in Java ?

Core Java

Ans. Likewise classes, methods also provide a way for code reuse and abstraction. Code is reused, clean and easy to understand if classified properly within classes and methods.

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Q492. Why it's a good practice to expose member elements through getter methods ?

Design

Ans. Encapsulation and Polymorphism.

We need methods to access variables in a polymorphic way as overriding only happens with methods and not with variables. Moreover getter provides a way to minimally open the access window for the object and hence provides better encapsulation. To add to those, we can have validation in the getter method before returning elements.

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Q493. Find the third last element in a linked list ?

Data Structure

Ans. First Find the number of nodes in the linked list and take it as n.then find the data at n-3 element.

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Q494. Why can't we create an instance of abstract class ? Why is it restricted by compiler ?

Core Java

Ans. Because Abstract class is incomplete i.e there are abstract methods that needs to be defined by extending classes.

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Q495. Why do we need polymorphism in Java ?

Core Java

Ans. Frankly saying I dont see much use of method overloading as its just little design convenience as you can use the same name but still have binding to different methods depending on the need.

Method overriding is really important and is much more useful than method overloading. Along with other programming concepts like interfaces and dependency injection , it facilitates the development of software as libraries and plug-gable components.

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Q496. What is the difference between a keyword and a modifier ?

Core Java

Ans. Keywords are the reserved words that have a pre defined meaning for a compiler whereas modifiers are the type of keywords that modifies the state or definition of a programming construct.

for, while are keywords but not modifiers.
private , public , final , abstract etc are keywords as well as modifiers.

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Q497. In which cases using SOAP is preferred over REST ?

Web Service

Ans. SOAP services are better in case we need to establish a formal and detail contract with the client or callers and hence suitable for

1. Services published for much wider unknown audience
2. Require large input payload
3. Requiring different level for authentication

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Q498. What is the difference between keywords, identifiers and literals in java ?

Core Java

Ans. Keywords are the reserved words that have a pre defined meaning for the compiler and hence are restricted to be used as identifiers.

Identifiers are the name assigned to different programming constructs like classes, interfaces, methods , variables etc.

Literals are the values that are assigned to Identifiers.

For example

int count = 0;

in the above statement "int" is a keyword, "count" is an identifier and "0" is a literal

Sample Code for keywords

Sample Code for identifiers

Sample Code for literals

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Q499. How does java identifies which method to be called in method overriding or runtime polymorphism, when both methods share the same name and signature ?

Core Java

Ans. Java identifies the method to be called at runtime by the object that is being referenced.

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Q500. What are some uses of interceptors ?

Java EE

Ans. Authentication / Authorization
URL forwarding
Auditing / Logging
Localization

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