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Q121. Which of the following is dependency exclusion ?

a. A doesn't depend on C and then A marks C as excluded.
b. A Depends on B and B depends on C and then A can mark B as excluded.
c. A and B depends on C and then they can mark C as excluded.
d. A depends upon B and B depends upon C then A marks C as excluded.

Maven

Ans. A depends upon B and B depends upon C then A marks C as excluded.

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Q122. Which of the following doesn't extend Collection interface ?

a. Set
b. List
c. Map
d. Queue

Core Java

Ans. Map

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Q123. What will happen if we don't have termination statement in recursion ?

Ans. Function call allocates a stackframe in stack. Every stackframe will use some memory to store local variables, parameters and to remember return address. Without terminating condition stackframes will keep consuming memory from stack and eventually program will result in stackoverflow error.

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Q124. In which cases , moving methods to utility class could be useful ?

Core Java

Ans. It could be worthy to move a method to util class if the method needs to be shared, doesn't require polymorphic behavior and need not be overridden in special cases.

Don't belong to one group through is-a relationship ( You can share through parent class method )

Don't implement a specific interface ( java 8 default methods )

Doesn't involve complex computing as you will be loosing the benefit of object state with just static method.

Doesn't require polymorphic behavior as static methods don't participate in runtime polymorphism.

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This question can be asked in different variants like performace improvement of an application, improving performance for DB communication etc.

Q125. What are the ways in which execution time of the code can be improved ?

Solution

Ans. This depends on entirely upon the code type. For example

1.If its just logic, we can try it to short circuit or put the if / switch case with maximum probability in the beginning.

2. Can use faster data structures, for eg - random retrieval instead of sequence / iterator

3. Working with primitive types or even bytes instead of Objects, even though it may result in marginal improvement.

4. If its service call, then service call with bulk load can help

5. If DB Operation, then with use of Indices , Views or using ORM , cache etc.

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Q126. Difference between GET and POST Requests ?

Web Service

Ans. GET is supposed to get information from the server. Client sends the minimal information so that Server can respond with the response body on basis of request. For example - You want to get complete employment record for employee id 123

POST is supposed to send the information for submission. Payload or a Body is usually sent so that it can be persisted on the server. For example - Sending the complete information of an employee ( id, name , dept etc ) to the server for persisting it.

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Q127. What is coupling and Cohesion ?

Design

Ans. Coupling is the degree of interdependence between software modules, a measure of how closely connected two modules are or the strength of the relationships between modules.

Cohesion refers to the degree to which the elements of a module belong together. Cohesion measures the strength of relationship between pieces of functionality within a given module.

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Q128. Why java doesn't support multiple Inheritance ?

or

Explain Java Diamond Problem.

Core Java

Ans. class A {
void test() {
System.out.println("test() method");
}
}

class B {
void test() {
System.out.println("test() method");
}
}

Suppose if Java allows multiple inheritance like this,

class C extends A, B {
}

A and B test() methods are inheriting to C class.

So which test() method C class will take? As A & B class test() methods are different , So here we would Facing Ambiguity.

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Usually asked to entry level software developers.

Q129. Write a program to swap two variables without using third

Core Java

Ans. public static void main(String[] args) {
   int num1 = 1;
   int num2 = 2;
   num1 = num1^num2;
   num2 = num1^num2;
   num1 = num1^num2;
   System.out.print("num1 = " + num1 +", num2 = "+num2);
}

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Q130. Can we overload method as following ?

void method(int... x){};
void method(int[] x){};

Core Java

Ans. No. Because java internally treats var args as arrays and hence both method declarations will generate the same byte code and hence would result in ambiguity while determining call binding.

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Q131. What are the benefits of Dependency Injection or IOC ?

Design

Ans. Central place for configuring dependencies.

No need to create object, container manage all this By using Run time polymorphism and association.

Facilities development of framework / libraries by injecting implementation classes in the implementation code.

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Q132. Differences between class not found exception and noclassdef found error ?

Core Java

Ans. ClassNotFoundException is an exception that occurs when we try to load a class at run time using Class.forName() or loadClass() methods and mentioned classes are not found in the classpath.

NoClassDefFoundError is an error that occurs when a particular class is present at compile time, but was missing at run time.

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Q133. serialization and deserialization of singleton class

Core Java

Ans. The problem with serialized singleton class is that whenever we deserialize it, it will create a new instance of the class. To overcome this scenario all we need to do is to provide the implementation of readResolve() method.

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Q134. What is the cost of using Cloud Formation ?

Amazon Web Services (AWS)

Ans. Cloud Formation does not have any additional cost but you are charged for the underlying resources it builds.

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Q135. Which region is the latest and most popular in AWS ? What are the advantages and disadvantages of using this region ?

Amazon Web Services (AWS)

Ans. US-East Virginia

This is the oldest and most popular region. All new features are rolled first in this region and hence they are first available there. The downside is that because of experimentation with new services, unavailability time is quite high.

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Q136. What are the advantage of having Edge Locations ?

Amazon Web Services (AWS)

Ans. It saves Network traffic and facilitates faster delivery by hosting bulk media and cached data near to client.

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Q137. Which AWS services would you use if you have find a cheapest solution for an analytics application ?

Amazon Web Services (AWS)

Ans. Computation

Spot Price Plan
F1 or P3 Instance Type
Cold Hdd (SCI ) EBS Volume

Storage

S3-IA

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Q138. There is a server which is 90% full, I need to increase the space. How can I do it ?

Server

Ans. Firstly ,we have removed old backup data from server after that we are checking which user consume high memory through df command.

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Q139. What is JSON ?

Json

Ans. JSON is "JavaScript Object Notation", primarily used for client-server or server-server communication. Its a much lighter and readable alternative to XML. JSON is language independent and is easily parse-able in all programming languages.

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Q140. Which data types are supported by JSON ?

Json

Ans. Number
String
Boolean
Array
Object
null

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Q141. Is tomcat an application or Web server ?

Server

Ans. Tomcat is a web server and a Servlet container. It is often used as an application server for web-based applications but does not include the complete suite of capabilities that a Java EE application server would supply.

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Q142. What is meant by an "asynchronous event." Give some examples ?

Operating System

Ans. An asynchronous event is one that occurs at an unpredictable time outside the control of the program that the CPU is running. It is not "synchronized" with the program.

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Q143. Give an Example of Annotations ?

Ans. Suppose that a software group traditionally starts the body of every class with comments providing important information:
public class Generation3List extends Generation2List {

// Author: John Doe
// Date: 3/17/2002
// Current revision: 6
// Last modified: 4/12/2004
// By: Jane Doe
// Reviewers: Alice, Bill, Cindy

// class code goes here

}
To add this same metadata with an annotation, you must first define the annotation type. The syntax for doing this is:
@interface ClassPreamble {
String author();
String date();
int currentRevision() default 1;
String lastModified() default "N/A";
String lastModifiedBy() default "N/A";
// Note use of array
String[] reviewers();
}
The annotation type definition looks similar to an interface definition where the keyword interface is preceded by the at sign (@) (@ = AT, as in annotation type). Annotation types are a form of interface, which will be covered in a later lesson. For the moment, you do not need to understand interfaces.
The body of the previous annotation definition contains annotation type element declarations, which look a lot like methods. Note that they can define optional default values.
After the annotation type is defined, you can use annotations of that type, with the values filled in, like this:
@ClassPreamble (
author = "John Doe",
date = "3/17/2002",
currentRevision = 6,
lastModified = "4/12/2004",
lastModifiedBy = "Jane Doe",
// Note array notation
reviewers = {"Alice", "Bob", "Cindy"}
)
public class Generation3List extends Generation2List {

// class code goes here

}

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Q144. What are few of the Annotations pre defined by Java?

Ans. @Deprecated annotation indicates that the marked element is deprecated and should no longer be used. The compiler generates a warning whenever a program uses a method, class, or field with the @Deprecated annotation.

@Override annotation informs the compiler that the element is meant to override an element declared in a superclass.

@SuppressWarnings annotation tells the compiler to suppress specific warnings that it would otherwise generate.

@SafeVarargs annotation, when applied to a method or constructor, asserts that the code does not perform potentially unsafe operations on its varargsparameter. When this annotation type is used, unchecked warnings relating to varargs usage are suppressed.

@FunctionalInterface annotation, introduced in Java SE 8, indicates that the type declaration is intended to be a functional interface, as defined by the Java Language Specification.

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Q145. What are meta Annotations ?

Ans. Annotations that apply to other annotations are called meta-annotations.

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Q146. Name few meta-annotations ?

Ans. @Retention annotation specifies how the marked annotation is stored:

@Documented annotation indicates that whenever the specified annotation is used those elements should be documented using the Javadoc tool. (By default, annotations are not included in Javadoc.)

@Target annotation marks another annotation to restrict what kind of Java elements the annotation can be applied to.

@Inherited annotation indicates that the annotation type can be inherited from the super class. (This is not true by default.) When the user queries the annotation type and the class has no annotation for this type, the class' superclass is queried for the annotation type. This annotation applies only to class declarations.

@Repeatable annotation, introduced in Java SE 8, indicates that the marked annotation can be applied more than once to the same declaration or type use. For more information, see Repeating Annotations.

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Q147. What is a Final Method ?

Core Java

Ans. A Method that cannot be overriden in the sub class.

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Very Frequently asked.Favorite question in Walk in drive for many Indian service companies.

Q148. What is a Final Class ?

Ans. A Class that cannot be sub classed.

Sample Code for final class

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Very frequently asked. Usually asked with questions related to String. Frequently asked at CTS / Cognizant

Q149. What is an Immutable Object ?

Core Java

Ans. Object that can't be changed after instantiation.

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Q150. Name few Java Exceptions ?

Core Java

Ans. IndexOutofBoundException ,
NoClassDefFoundException ,
OutOfMemoryException ,
IllegalArgumentException,
NullPointerException,
IllegalStateException

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