Interview Questions and Answers for 'T' | Search Interview Question

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Q1171. Does it make sense to have return statement at the end of method ?

Ans. It make sense if its returning something. It doesnt make sense for void methods where return statement is not preceded by anything. In case of void methods , return as last statement has no impact and is actually a overhead.

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Q1172. How to specify the or/and combination restrictions within Criteria in Hibernate ?

Hibernate

Ans. session.createCriteria(Employee.class).add( Restrictions.or(Restrictions.like("name", "A%"),Restrictions.like("name", "B%"))).list();

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Q1173. Difference between Maven Project and Module ?

Maven

Ans. Maven Module has a Parent whereas Project doesnt. when we add the parent section to the pom file, it adds the module section to the parent project pom file. When we execute mvn compile / install, it basically checks that module section of the parent to identify all the modules that needs to be compiled first.

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Q1174. What is meant by following error ?

Source folder is not on the Java build class path

Core Java

Ans. It means that the respective folder is not looked upon by Java to look for java or resource files and hence not being included as part of build.It needs to be added to Java Build Path.

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Q1175. What is the use of .project file in eclipse ?

Tool

Ans. .project is a project description file that helps plugins and eclipse understand about the project - organization of projects , their names, builders used by them etc.

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Q1176. What is a .classpath file in eclipse ?

Tool

Ans. .classpath specifies the source java and resource folders that are used by Builders to build.

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Q1177. What is a shutdown hook ?

Core Java

Ans. Shutdown hook is a thread that is invoked implicitly by JVM just before the shut down. It is used to clean up unused resources.

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Q1178. Can we start the same thread twice ?

Core Java

Ans. No we cannot start the same thread twice. Each thread has a lifecycle.

But Yes, we can run the same code in parallel using different threads.

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Q1179. Write an Algorithm for Graph Traversal ? The Graph has a loop.

Algorithm

Ans. Please not that all such questions can be easily answered through recursion.

Simple recursive implementation could be

traverse(root);

void traverse(Element element){
if(element.hasNext()){
traverse(element.next());
} else {
System.out.println(element);
}
}

but this algo / code lead to endless loop if there is a loop in graph traversal.

So you can keep a collection to keep track of which elements have laready been traversed

static List<Elements> listOfAlreadyTraversedElements = new ArrayList<Elements>();

main(){
traverse(root);
}

void traverse(Element element){
if(element.hasNext()){
traverse(element.next());
} else {
listOfAlreadyTraversedElements.add(element);
System.out.println(element);
}
}

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Q1180. How is String class unique ?

Core Java

Ans. String class is immutable as well as final. Because of these properties , String objects offer many benefits

1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references.

Example -

String str1 = "String1";
String str2 = "String1"; // It doesnt create a new String and rather reuses the string literal from pool

// Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too

2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence its not fit to be cached.

3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment.

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Q1181. Explain Agile Software Development Methodology ?

Process

Ans. https://en.wikipedia.org/wiki/Agile_software_development

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Q1182. Difference between JDBC and Hibernate ?

Database

Ans. JDBC is a standard Java Api for Database communication whereas Hibernate is an ORM framework that uses JDBC to connect with Database.

Hibernate is another layer of object table mapping over JDBC that provide a database independent, object oriented and an efficient way of database communication.

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Q1183. Have you ever tried mocking static methods ?

Testing

Ans. Yes, that can be done using Power Mock. Mockito doesnt provide a way to mock static methods.

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Frequently asked in Alibaba (Based on 2 feedback)

Q1184. What is the best Memory setting for JVM ?

Core Java

Ans. In Java JVM memory settings is done by use the arguments -Xms -Xmx. Use M or G after the numbers for indicating Megs and Gigs of bytes respectively. -Xms indicates the minimum and -Xmx the maximum.

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Q1185. Difference between relational databases and NoSQL databases ?

Database

Ans. https://www.mongodb.com/scale/nosql-vs-relational-databases

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Q1186. How would you process a 20 gb file with an application only having access to 4gb memory ?

BigData

Ans. Load the file in chunks and then process. If we need to do analytic, we can process analytic information for those chunks and then reprocess the processed information from each chunk.

For example - we need to average all marks in the file. We can divide the file and load into 5 chunks and calculate average for each chunk. Then we can collect averages for all 5 chunks and then calculate the final average.

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Q1187. What is a web service ?

Java EE

Ans. A Web service is a service offered by one system to another, for communication over web through http. XML are JSON are usually used for sending across information from one system to another.

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Q1188. Write Delegate function of JQuery ?

JQuery

Ans. http://www.w3schools.com/jquery/event_delegate.asp

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Q1189. What is the difference between http and https ?

Java EE

Ans. https encrypts the data using SSL whereas http sends it as plain text, So https is secure protocol whereas http is not.

Moreover https connects on port 443, while HTTP is on port 80

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Q1190. Implement an LRU Cache ?

Design

Ans. https://www.programcreek.com/2013/03/leetcode-lru-cache-java/

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Q1191. Flatten a Binary Tree to Linked List

Algorithm

Ans. https://www.geeksforgeeks.org/flatten-a-binary-tree-into-linked-list/

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Q1192. How to delete duplicate elements in a table ?

Database

Ans. DELETE FROM TABLE WHERE ROW_NUM NOT IN ( SELECT MAX(ROW_ID) FROM TABLE GROUP BY DUPLICATE_FIELD )

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Q1193. Write a Program to print permutations of a String.

Core Java

Ans. public static Stream permutations(String str) {
if (str.isEmpty()) {
return Stream.of("");
}

return IntStream.range(0, str.length()).boxed()
.flatMap(i -> permutations(str.substring(0, i) str.substring(i 1)).map(t -> str.charAt(i) t));

}

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Q1194. How to create stateful Rest Services ?

Rest

Ans. There is no direct way to make stateful REST service but when first time request send to server, generate the token on server and send back to client. When every time new request is send the token is send to identify the request is coming from same client.

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Q1195. Difference between Array and ArrayList ?

Core Java

Ans. <a href="http://javahungry.blogspot.com/2015/03/difference-between-array-and-arraylist-in-java-example.html" rel="nofollow">http://javahungry.blogspot.com/2015/03/difference-between-array-and-arraylist-in-java-example.html</a>

Sample Code for ArrayList

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Q1196. Difference between Error and Exception ?

Core Java

Ans. An Error indicates serious problems that a reasonable application should not try to catch whereas

An Exception indicates conditions that a reasonable application might want to catch.

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Frequently asked in Accenture.

Q1197. What is your biggest achievement at work ?

General

Ans. [Open Ended Answer]

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Q1198. What will be the crontab to run a job every last day of month ?

Unix

Ans. 59 23 28-31 * * [ "$(date +%d -d tomorrow)" = "01" ] && job_name

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Q1199. Write a unix command to find top 10 files by size ?

Unix

Ans. du -a /var | sort -n -r | head -n 10

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Q1200. What are fields that gets displayed when you execute "Top" command and briefly explain each field ?

Unix

Ans. PID - process identification number is an identification number that is automatically assigned to each process when it is created

USER - User Name

PR - PR is the process actual priority

NI is the nice value, which is a user-space concept.

VIRT -Virtual Image (kb). The total amount of virtual memory used by the task.

RES - Resident size (kb). The non-swapped physical memory a task has used.

SHR - Shared Mem size (kb). The amount of shared memory used by a task.

S - Process Status. The status of the task which can be one of:

D = uninterruptible sleep
R = running
S = sleeping
T = traced or stopped
Z = zombie

%CPU - % CPU usage

%MEM - % MEM Usage

TIME - Total CPU time the task has used since it started.

COMMAND - Command which was used to execute the process

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