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Q61. what is the difference between collections class vs collections interface ?

Ans. Collections class is a utility class having static methods for doing operations on objects of classes which implement the Collection interface. For example, Collections has methods for finding the max element in a Collection.

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Q62. What are some Java related technologies used for distributed computing ?

Ans. sockets, RMI. EJB

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Q63. What are the components of J2EE ?

Ans. applets
Client component like Client side Java codes.
Web component like JSP, Servlet WAR
Enterprise JavaBeans like Session beans, Entity beans, Message driven beans
Enterprise application like WAR, JAR, EAR

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Q64. What is the difference between comparable and comparator in java.util pkg?

Core Java

Ans. Comparable interface is used for single sequence sorting i.e.sorting the objects based on single data member where as comparator interface is used to sort the object based on multiple data members.

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Q65. Is it possible to compile and run a Java program without writing main( ) method?

Ans. Yes, it is possible by using a static block in the Java program.

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Q66. What is Externalizable interface?

Core Java

Ans. Externalizable is an interface which contains two methods readExternal and writeExternal. These methods give you a control over the serialization mechanism.

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Q67. Write a method to check if input String is Palindrome?

Core Java

Ans. private static boolean isPalindrome(String str) {

if (str == null)
return false;

StringBuilder strBuilder = new StringBuilder(str);

strBuilder.reverse();

return strBuilder.toString().equals(str);

}

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Q68. Write a Program to check if 2 strings are Anagrams ?

Core Java

Ans. public void checkIfAnagram(String str1,String str2){
boolean anagram = true;
for(char c:str1.toCharArray()){
if(!str2.contains(String.valueOf(c))){
System.out.println("Strings are Anagrams");
anagram = false;
}

if(anagram == true){
System.out.println("Strings are not Anagrams");
}
}
}

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Q69. Which of the following syntax is correct ?import static java.lang.System.*;or static import java.lang.System.*;

Core Java

Ans. import static java.lang.System.*;

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Q70. What are temp tables ?

Ans. These are the tables that are created temporarily and are deleted once the Stored Procedure is complete.

For example - we may like to pull some info from a table and then do some operations on that data and then store the output in final output table. We can store the intermediary values in a temp table and once we have final output with us, we can just delete it.

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Q71. Can we compose the Parent Class object like this ?

class BuggyBread1 extends BuggyBread2 {

private BuggyBread2 buggybread2;

public static void main(String[] args){
buggybread2 = new BuggyBread2();
}
}

Ans. Yes.

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Q72. Difference between jar , war and ear ?

Java EE

Ans. Jar is Java Archieve i.e compressed Class or Class / Java files.

War comprises of compressed Servlet class files,JSP FIles,supporting files, GIF and HTML files.

Ear comprise of compressed Java and web module files ( was files ).

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Q73. What is a package and what are its advantages ?

Core Java

Ans. Package is a namespace that organizes a set of related classes.

Advantages of Packages

1. Better Organization of classes.
2. Saves from the problem of duplicate names as duplicate class names are allowed across different packages.

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Q74. What is a self Join and give an example of a self Join ?

or

What is self Join and What is it's purpose ?

Database

Ans. When a Table Join itself , it's a Self Join. For example - we like to know the pair of department names where first dept has lesser employees than the later.

Select D1.name , D2.name from Dept D1, Dept D2 where D1.employee_count < D2.employee_count

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Q75. What are design situations to use Singleton and Prototype Design Pattern ?

Design

Ans. Both are creational design patterns.

Singleton is used when we would like to reuse an object if object is not supposed to hold request or thread specific information. Inversely Prototype is used in situations where we would like to reuse the object information but the request / thread may require it own data to be persisted.

In short, Singleton is used in situations where we can live with single object being shared across multiple requests or threads whereas Prototype is used when we need duplicate copies of objects.

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Q76. 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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Q77. 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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Q78. 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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Q79. What does import java.util.* means in java ?

Core Java

Ans. It means import all the classes and interfaces within java.util package and make them available to use within the current class or interface. This is shorthand wild card annotation for importing all classes within a particular package. This won't import the classes within the sub packages of java.util.

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Q80. 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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Q81. What are the reasons to choose between reserved and on demand instances ?

Server

Ans. In terms of compute options and configurations, Reserved Instances and On Demand instances are the same. The only difference between the two is that a Reserved Instance is one you rent (reserved) for a fixed duration, and in return you receive a discount on the base price of an On Demand instance.

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Q82. Can you explain the integration between API Gateway and Lambda if we wish to develop services using these tools.

Amazon Web Services (AWS)

Ans. We can create API gateway and give the name of lambda function in order to be linked with lambda function, deploy the API and whenever request will be made from API it will directly be linked to lambda function to perform further process.

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Q83. Why do we need to specify import statement ? Don't you think Java could have been designed in such a way to automatically import everything that's in the class path ?

Core Java

Ans. Java could design it in such a manner but would result in ambiguity if there are multiple files with the same name. The only way to get over it to show the message when you use any such class to provide explicit import with the package prefix. The other problem could be that Java might have to change the early import to Late import and check what's being used to decide what needs to be imported as otherwise you will see errors regarding the ambiguous imports with duplicate file name.

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Q84. 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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Q85. What would you do if you see an error thrown by a lambda function as "Access Denied" while doing something with S3 ?

Amazon Web Services (AWS)

Ans. Just like people , AWS resources too have execution roles or permissions. Seems like in such a situation Lambda function may not have sufficient privileges to perform operations on S3. For example - The execution role of Lambda may just have read permissions on S3 and we may be trying to perform PutObject operation.

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Q86. What are the drawbacks of using Spot EC2 instances ?

Amazon Web Services (AWS)

Ans. You cannot reserve the time slot and they can be made to use whenever they are available.

AWS can Terminate the EC2 instance on their own even if it's in use.

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Q87. What are the things to consider while provisioning computing in AWS ?

Amazon Web Services (AWS)

Ans. Service ( EC2, Lambda etc )
AMI ( Operating System and Softwares )
Instance Type ( T,M, R etc )
EBS ( Volume Type , Size )
Price Class ( OnDemand, Dedicated etc )

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Q88. What is the purpose of EC2 Health check ?

Amazon Web Services (AWS)

Ans. We can use this check for variety of things -

1. Monitoring the status / Alarms in case it's down
2. Regulating traffic to healthy instances only through Load Balancer

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Q89. What are the advantages and disadvantages of using Lambda over EC2 ?

Amazon Web Services (AWS)

Ans. Advantages -

Much Cheaper
Continuous scaling
Higher level and Serverless

Disadvantages -

Warm up time
Limited flexibility in terms of technologies
Limited control

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Q90. Can we associate a single EFS volume with multiple EC2 instances ?

Amazon Web Services (AWS)

Ans. Yes

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