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

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Q1211. With a Table employee having columns Id,Name,ManagerEmployeeId, Write a SQL to find the Manager with maximum number of employees ?

Database

Ans. Select Name from EMPLOYEE where ID in (Select ManagerEmployeeId from EMPLOYEE
Group By ManagerEmployeeId
order by count(Id)
LIMIT 1)

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Q1212. How to make sure that only one instance is created in Singleton Pattern ?

Core Java

Ans. public class SingleTon {
private SingleTon() {
if (singleTon != null) {
throw new RuntimeException("cant not create the object");
}
}
public Object clone() throws CloneNotSupportedException {
throw new CloneNotSupportedException("can not be create");
}

static private volatile SingleTon singleTon;
public static SingleTon getInstance() {
SingleTon singleTon = this.sample;
if (singleTon == null) {
synchronized (this) {
singleTon = this.singleTon;
if (singleTon == null) {
singleTon = this.singleton = new SingleTon();
}
}
}
return singleTon;
}
}

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Q1213. Can we have an entity in hibernate without primary Key ?

Hibernate

Ans. No, Every entity in hibernate needs to have a key, either primary or composite.

If we dont have a primary key on table, there are various ways this problem can be countered.

1. By using composite key on entity ( make sure that the appropriate unique constraint in defined on columns in Database )

2. By mapping Id in entity to ROWID of table.

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Q1214. Provide an implementation for Producer / Consumer using threads.

Core Java

Ans. https://www.tutorialspoint.com/javaexamples/thread_procon.htm

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Q1215. When should we use Abstract classes ?

Core Java

Ans. Abstract classes provide a mechanism of interfacing ( using abstract method ) as well as inheritance ( extending abstract class ). So they should be used in place of interfaces in case there is some code ( methods ) or object body ( member elements ) that can be reused with inheritance.

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Q1216. What is the difference between following code segments

1.

try {
for(int i=0;i<100;i++){
calculate(i);
}
} catch (Exception ex) {
System.out.println("Error while processing")
}

and

2.

for(int i=0;i<100;i++){
try {
calculate(i);
} catch (Exception ex) {
System.out.println("Error while processing")
}
}

Core Java

Ans. In first case the whole loop will terminate as soon as any exception happens in the method calculate ( assuming calculate method is not handling its exception and those are thrown back at the calling method )

In Second case exception will be caught for individual iteration and hence it wont break the loop and will continue for the next iteration.

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Q1217. What is the difference between ServletConfig and ServletContext ?

Java EE

Ans. http://www.java4s.com/java-servlet-tutorials/difference-between-servletconfig-and-servletcontext-in-java/

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Q1218. Explain some of the features of Java ?

Core Java

Ans. Object Oriented - Java is object oriented but isn't purely object oriented as we have primitives along with objects.

Platform Independent - As JVM provides the translation to the Machine code as per the underlying Operating System.

Interpreted as well as compiled - Java files are compiled as class files and then class files are interpreted by JVM.

Runs on a Virtual Machine - Which is JVM that acts as an independent sub environment.

Multi-threaded - As applications can run on single thread as well as multi thread.

Modularity - Through usage of Classes , methods and Interfaces.

Robust

Usage in variety of Application types - Web , Gaming, BigData.

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Q1219. Name some of the Java Keywords ?

Core Java

Ans. Static , Final , Synchronized, private , public , protected, volatile, transient, super, this,import , abstract,native,default (effective java 8), new

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Q1220. Which operators in Java have highest precedence ?

Core Java

Ans. Braces, i.e () and [] have the highest precedence

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Q1221. Which class is the root class of all Exceptions in Java ?

Ans. Throwable

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Q1222. What is MAC Address ?

Networking

Ans. A media access control address is a unique identifier assigned to network interfaces for communications at the data link layer of a network segment. MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet and Wi-Fi.

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Q1223. What is an exception and exception handling in Java ?

Core Java

Ans. An Exception in java is the occurrence during computation that is anomalous and is not expected.

Exception handling is the mechanism which is used to handle such situations.

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Q1224. What technical stuff you like to do in your free time ?

General

Ans. [Open Ended Answer]

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Q1225. What is a factory design pattern ?

Design

Ans. Factory Design Patterns is the pattern that recommends creation of separate Factory Object for creation of other object.

So its like saying - If you want to create an object of ClassA, Talk to FactoryObject ( which is an object of FactoryClass ). FactoryObject in itself encapsulates the inputs and logic required to make the decision regarding the creation and construction of object.

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Q1226. How is hashcode calculated in java ?

or

What are the rules for hashcode calculation ?

Core Java

Ans. General contract of hashCode is:

1.Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer,

2.If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.

3.It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results.

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Q1227. Why main method is declared static ?

Core Java

Ans. static is the keyword that makes it accessible even without creating any object and using class name only. Making it non static would like creation of object upfront before calling the method.

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Q1228. What is Spring Security ?

Spring

Ans. Spring Security is a powerful and highly customizable authentication and access control framework. It is the de facto standard for securing Spring-based applications.

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Q1229. Create a Class Bank with the methods to deposit and Withdraw ?

Core Java

Ans. class Bank {
int balance;

Bank(){
balance = 0;
}

void deposit(int amount){
balance = balance amount;
}

int withdraw(int amount){
balance = balance - amount;
return balance;
}
}

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Frequently asked in high end product companies.

Q1230. Write code for LRU Cache

Core Java

Ans. https://www.geeksforgeeks.org/lru-cache-implementation/

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Q1231. Explain your experience with Java, spring and web services?

General

Ans. Have worked on Java 7 and Java 8, In Java 8 , Worked with streams , lambda expression and default methods.

Have worked on both Spring Mvc and Spring Boot, using Spring dependency injection, Rest services , AOP , JDBC and Hibernate integration.

Have worked on Rest services using Spring and Spring Boot. Have worked on SOAP web services too.

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Q1232. Can a constructor throw an exception ?

Core Java

Ans. Yes

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Q1233. Can constructor be synchronized in Java ?

Core Java

Ans. No, constructors can not be synchronized in Java. In fact using the keyword synchronized with a constructor results in compilation error.

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Q1234. Will finally run if we have return statement and it exits the method early ?

Core Java

Ans. finally will execute in all graceful situations - graceful executions as well as graceful exceptions. The only situation when finally block won't execute is when the app is abruptly stopped, killed or unplugged.

Sample Code for finally

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Q1235. Is there any relationship between Web.xml and Spring.xml ?

Spring

Ans. No, there is no relationship between web.xml and spring.xml but you have to configure spring.xml in web.xml in order initialize beans when application starts up

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Q1236. Why do you wan to stay in IT ?

General

Ans. Coding , Science and Mathematics has always fascinated me. I have curious mindset that continuously look for solutions.

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Q1237. How to make sure that no request are lost in client server application ?

Solution

Ans. By keeping some sort of storage at the client side for each request and then matching it up against the response received to make sure that the request was well received.

A queue can be used for this purpose.

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Q1238. Scale yourself on Java on the scale of 1 to 10

General

Ans. [Open Ended Answer]

The objective of the question is to check how efficient one is in the language so that appropriate level questions are asked. Don't tell too high number if you are being interviewed for a junior or mid level position as the interviewer may throw advance level questions.

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Q1239. Is it mandatory to have a default constructor ?

Core Java

Ans. No.

Default constructor is provided by compiler if no constructor is provided ( argument or no argument ) by us.

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Try 1 Question(s) Test

Q1240. What is the problem with this code

double x=10.04;
int a = x;

Ans. It will give an error saying 'cannot convert from double to int'

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