Interview Questions and Answers - Basic Level | Search Interview Question

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Q91. Which are the sorted collections ?

Core Java

Ans. TreeSet and TreeMap

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Very frequently asked if being interviewed for hibernate. Frequently asked in Tata Consultancy (TCS) and Overstock.com

Q92. Difference between load and get ?

Hibernate

Ans. If id doesnt exist in the DB load throws an exception whereas get returns null in that case.get makes the call to DB immediately whereas load makes the call to proxy.

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Q93. When does an application throw NullPointerException ?

Core Java

Ans. When it tries to access an object element or method using reference which is actually null.

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Q94. How is Abstraction implemented in Java ?

Core Java

Ans. Abstraction is provided in Java by following ways -

Coding to the ( Interfaces / Abstract Classes ) or contracts

By Encapsulating details within classes and exposing the minimal Door ( few public methods )

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Q95. 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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Q96. Which java frameworks have you used ?

General

Ans. I have primarily worked on Web applications and hence worked on Struts , Spring , Hibernate, JSF ( Java Server Faces ) , Velocity etc.

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Q97. How are values passed in Java ? By value or reference ?

Core Java

Ans. Java only provides pass by value.

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Q98. 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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Q99. What is a Database Trigger ?

Database

Ans. A trigger is a special kind of stored procedure that automatically gets executed upon an event in the database server.

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Q100. 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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Frequently asked.

Q101. When does the finally block gets executed ?

Core Java

Ans. A finally block of code always executes, whether or not an exception has occurred.The only time finally won't be called is if you call System.exit() or if the JVM crashes first.

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Q102. Explain System.out.println ?

Core Java

Ans. System is a class within java.lang package that contains several useful class fields and methods. It cannot be instantiated and hence can use only statically.even in this case this has been used statically i.e with class name itself and without creating an instance.

out is the static reference of Printstream declared as following in the System Class -

public final static PrintStream out = null;

println is the method of PrintStream class.

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Q103. Does java supports operator overloading ?

Core Java

Ans. No

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Q104. What is the use of static keyword in Java ?

Core Java

Ans. static keyword is used to specify that the respective programming construct ( method , variable ) belongs to the class and not to its instance and is supposed to be shared by all instances of the class.

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Q105. Explain various Searching and Sorting Algorithms ?

Algorithm

^{This question was recently asked at 'HeadStrong,ServiceNow'.This question is still unanswered. Can you please provide an answer.}

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Q106. What is a Servlet Filter ?

Java EE

Ans. It's an object that can intercept http request and response and hence we can take appropriate action on those requests.

There are different types of filters based on Specifications like

Authentication
Logging
Encryption
Tokenizing

etc

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Q107. What is the difference between authentication and authorization ?

Authentication

Ans. Authentication is the process of verifying the identity and credentials of the user to authenticate him into the system.

whereas

Authorization is the process by which access to a segment , method or resource is determined.

Authorization is usually a step next to authentication.

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Q108. What access the variable gets if we don't provide any access specifier ?

Core Java

Ans. It gets the default access i.e package protected.

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Q109. How does java identifies which method to be called in method overriding or runtime polymorphism, when both methods share the same name and signature ?

Core Java

Ans. Java identifies the method to be called at runtime by the object that is being referenced.

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Q110. What are the types of authentication used in Web services ?

Web Service

Ans. Encrypted User Name / Password
Encrypted Password within Cookie
Encrypted Tokens
IP
Client Certificates
Oauth

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Q111. Write code to create a folder if it doesn't exist.

Core Java

Ans. File folder = new File(path);

if(!folder.exists()){
try {
folder.mkdir();

} catch (Exception e) {}
}

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Q112. Difference between Arrays and ArrayList ?

Core Java

Ans. Both Arrays and ArrayLists are used to store elements. Elements can be either primitives or objects in case of Arrays, but only objects can be stored in Arraylist. Array is a fixed length data structure while arraylist is variable length collection class. Once created, you cannot change the size of the arrays, but arraylists can dynamically resize itself when needed.Another notable difference between Arrays and Arrayslist is that arary is part of core java programming and array list is part of collection classes

Sample Code for arrays arraylist

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Q113. What is a cookie ?

Java EE

Ans. A cookie is a small piece of text stored on a user's computer by the browser for a specific domain. Commonly used for authentication, storing site preferences, and server session identification.

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Q114. Can static method access instance variables ?

Core Java

Ans. Though Static methods cannot access the instance variables directly, They can access them using instance handler.

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Very frequently asked. Usually asked in this format or as difference with interfaces / concrete classes.

Q115. What is an abstract class ?

Core Java

Ans. Abstract class is the class that is not supposed to be instantiated. The purpose of the class to only have extension to the derived class.

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Q116. Which interface does java.util.Hashtable implement?

Core Java

Ans. Java.util.Map

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Frequently asked.

Q117. What is an Iterator?

Core Java

Ans. Iterator is an interface that provides methods to iterate over any Collection.

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Q118. Which interface provides the capability to store objects using a key-value pair?

Core Java

Ans. java.util.map

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Q119. Why java doesn't support multiple Inheritence ?

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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Frequently asked to fresh graduates.

Q120. What is the difference between yield() and sleep()?

Operating System

Ans. When a object invokes yield() it returns to ready state. But when an object invokes sleep() method enters to not ready state.

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