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

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Q571. What will the following print upon executing main method of Main class ?

public class BaseClass {
BaseClass(){
System.out.println("Hello I am in Base Class Constructor");
}
}

public class DerivedClass extends BaseClass{
DerivedClass(){
System.out.println("Hello I am in Derived Class Constructor");
}
}

public class Main {

public static void main(String[] args) {
DerivedClass derivedClass = new DerivedClass();
}
}

Core Java

Ans. Hello I am in Base Class Constructor
Hello I am in Derived Class Constructor

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Q572. Will it print the message in Base Class constructor if we execute main method of Main class ? why ?

public class BaseClass {
BaseClass(){
System.out.println("Hello I am in Base Class Constructor");
}
}

public class DerivedClass extends BaseClass{
}

public class Main {

public static void main(String[] args) {
DerivedClass derivedClass = new DerivedClass();
}
}

Core Java

Ans. Yes.

When the Derived class constructor is initialized , a no argument super will be called intrinsically.

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Q573. Does it make sense to verify a method call if we already have a mock for it.

For example -

Mockito.when(a.callMethod()).thenReturn(1);
verify(a.callMethod()); // Does it make sense

Mockito

Ans. There is no guarantee that the mock will get called as callMethod may never get called. Verify is to make sure that the method gets called. Mock is it return 1 if the method gets called so they both are kind of independent things.

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Q574. Do you use Mockito's generic any method or just prefer to use specific arguments ?

Mockito

Ans. It depends on the data type, we use as the parameter.
If it is a simple data type and we validate the input, we may use specific arguments.
Else, we can go for the generic any

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Q575. Do you like working on IntelliJ ? How is it different than Eclipse ?

IntelliJ

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Q576. What is the purpose of doing mvn eclipse:eclipse or man idea:idea

Maven

Ans. It is an instruction to maven to set up files ( class path , project ) within the IDE

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Q577. Tell me about thread pool?

Design

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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Q578. Isnt the use of HashTable and ConcurrentHashMap the same, i.e providing synchronized map collection ?

Core Java

Ans. Both provide the thread safety but the actual difference come when talk about performance. CHM gives best performance when no of writer threads are less in number.

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Q579. What are the features of Spring Framework ?

Spring

Ans. Core technologies: dependency injection, events, resources, i18n, validation, data binding, type conversion, SpEL, AOP.

Testing: mock objects, TestContext framework, Spring MVC Test, WebTestClient.

Data Access: transactions, DAO support, JDBC, ORM, Marshalling XML.

Spring MVC and Spring WebFlux web frameworks.

Integration: remoting, JMS, JCA, JMX, email, tasks, scheduling, cache.

Languages: Kotlin, Groovy, dynamic languages.

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Q580. Can we use try within catch block ?

Core Java

Ans. Yes

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Q581. Which s/w is used for adhar card verification for amount transfer?

Ans. The Aadhaar enabled Payment System or AePS

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Q582. Is java fully platform independent ?

Core Java

Ans. yes, Java is a class-based and object-oriented programming language. It is a platform-independent language i.e. the compiled code can be run on any java supporting platform. It runs on the logic of “Write once, run anywhere”.

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Q583. 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.

Design

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Q584. Does Java SE has Immutable collections ?

Core Java

Ans. Yes wef from Java 9

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Q585. Can we mock static methods using Mockito ?

PowerMock

Ans. No, We can use PowerMock for that.

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Q586. Where to use interface and abstract class ?

Core Java

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Q587. Write a java program to find the maximum profit in day trading

Core Java

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Q588. How do you usually choose which type of EC2 Instance you would like to Use ?

Amazon Web Services (AWS)

Ans. Depend on its pricing module

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Q589. What is Bastion host ?

Infrastructure

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Q590. What is TypeCasting ?

Core Java

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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Q591. In what terms Java is better language than c and c++ ?

Ans. Java manages pointers intrinsically and gives no control over pointer arithmetic to coders and hence saves the applications from many possible problems like dangling pointers and memory leaks.

Java is platform independent and hence any application can be run on any hardware with the suitable JVM without building it separately for different hardwares.

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Q592. Are you willing to spend long hours ?

General

Ans. why not if getting money in dollars!

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Q593. Find all files from a directory (including sub directories ) that could contain dates in a specific format.

Unix

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Q594. Do you think it's a good practice to perform releases from a branch and then merge code to the master ?

SCM

Ans. We have followed this practice in one of the project. The only downside we felt was the need to merge the new snapshot version to master after the release.

The Benefit is that it's easy to just ignore the branch if complete rollback happens and hence master remains in sync with production.

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Q595. How do you branch your code within SCM ?

SCM

Ans. We keep a Working Branch , Release Branch and Master.

Working Branch is what we work on. We release from the release branch.

So the flow for merge is

Work Branch -> Release Branch -> Master

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Q596. Will this give compile time error ?

Object[] strArray = new String[2];
strArray[0] = 5;

Core Java

Ans. No. But It will throw ArrayStoreException at runtime.

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Q597. If arrays cannot be resized , Why is this code valid

String[] strArray = new String[2];
strArray = new String[5];

Core Java

Ans. We are not resizing the first array here but assigning the reference strArray to a new Array with size 5.

So after line 2, We have 2 arrays in memory, one with size 2 and other with size 5 with strArray referring to second array with size 5.

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Q598. Is this code valid

String[] strArray = new String[2];
strArray.length = 5;

Core Java

Ans. It will give compile time error saying "The final field array.length cannot be assigned"

Arrays once initialized cannot be resized.

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Q599. Is this array initialization correct ? If Yes, What will be the size of array ?

String[] strArray = new String[3]{"Buggy","Bread"};

Core Java

Ans. No. It will result in error saying "Cannot define dimension expressions when an array initializer is provided"

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Q600. Is this array initialization correct ? If Yes, What will be the size of array ?

String[] strArray = new String[]{"Buggy","Bread"};

Core Java

Ans. Yes, size of the array will be 2.

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