How to Fix java.lang.classnotfoundexception oracle.jdbc.driver.oracledriver [Solved]

Scenario : Your Java program, either standalone or Java web application is trying to connect to Oracle database using type 4 JDBC thin driver "oracle.jdbc.driver.oracledriver", JVM is not able to find this class at runtime. This JAR comes in ojdbc6.jar or ojdbc6_g.jar which is most probably not available in classpath.

Cause : When you connect to Oracle database from Java program, your program loads the implementation of Driver interface provided by the database vendor using class.forName() method, which throws ClassNotFoundException when driver class is not found in classpath. In case of Oracle the driver implementation is oracle.jdbc.driver.oracledriver and "java.lang.classnotfoundexception oracle.jdbc.driver.oracledriver" error indicate that this class is not available in classpath. Since this class is bundled into ojdbc6.jar, its usually the case of this JAR not present in Classpath

How to Set Specific Java Version for Maven in Windows? Example Steps

Maven is a great build tool and most of the Java developer uses Maven to build their projects, but like any other tool, there are some intricacies which you need to know while using it. One of them is that Maven uses the Java version from the JAVA_HOME environment variable and not the PATH environment variable. If you have multiple JDK installed on your machine and getting an Unsupported major.minor version 51.0 or Unsupported major.minor version 52.0 error while building your project but have right Java version in PATH then you may need to check the JAVA_HOME and update it. If you don't have access to do it then you can still change JAVA_HOME using the set command in your local shell and run the Maven's mvn command to build the project

Difference between WHERE and HAVING clause in SQL? Example

The main difference between the WHERE and HAVING clauses comes when used together with the GROUP BY clause. In that case, WHERE is used to filter rows before grouping, and HAVING is used to exclude records after grouping. This is the most important difference, and if you remember this, it will help you write better SQL queries. This is also one of the important SQL concepts to understand, not just from an interview perspective but also from a day-to-day use perspective. I am sure you have used the WHERE clause because it's one of the most common clauses in SQL along with SELECT and used to specify filtering criteria or conditions.

Google Data Analytics Professional Certificate Review

Data analysis is almost the same as data science. Still, it deals less with machine learning and artificial intelligence and focuses more on generating insight into the company data by connecting patterns and trends with the company goal. The concept of data analysis is not actually new, and people are using this science hundred of years ago, but the concept becomes famous when computers come to life in the last decade.

Data analytics helps marketers and companies understand their customer’s behavior, so they can decide what’s good offers to drive to them and transform the education, healthcare industry, and many more, to name a few. Learning data science is not that hard since you will not understand many programming languages or deal with artificial intelligence.

Hence, if you plan to have these skills in under six months, you should probably take this program called Google Data Analytics Professional Certificate offered by Google through the Coursera platform.

1. The Instructors Review

This specialization offers by an initiative called Grow With Google, which last collaborates with different schools, universities, and organizations to launch courses that teach people digital skills such as programming, marketing, data analysis, and more. They have gained millions of students worldwide since 2017, which is the year this initiative has come to live.

2. Course Content

2.1. Foundations: Data, Data, Everywhere

This first section will teach you how data analysis uses data analytics to make decisions for their companies and how analytical thinking can drive decision-making. Later you will learn about the data phases and tools used by data analytics and exploring some of the tools used by data analytics, such as SQL and spreadsheets. Finally, learn the specific job that these people do for their businesses.

2.2. Ask Questions to Make Data-Driven Decisions

Before you analyze your data, you have to ask some questions that you have to answer by analyzing your data to learn the common analysis challenges and how to address them. Next, you will explore all kinds of data you will face during your journey in the data analysis and share this through reports and dashboards and explore how data analysis uses spreadsheets in their daily routine.

2.3. Prepare Data for Exploration

You will start by learning how people generate their data and how you, as a data analyst, will decide which data to collect for your analysis. You will also learn how to identify the different bases in your data and extract data from the database. Finally, you will learn how the organization keeps the data safe and secure.

2.4. Process Data from Dirty to Clean

You will learn why data integrity is so important for successful decision-making and discovering the different data structures. Before you start analyzing data, you have to clean it first, so this section will teach you the different tools used to clean the data, such as using SQL language. Finally, you will find out the process of verifying and reporting data cleaning.

2.5. Analyze Data to Answer Questions

You will begin by understanding the importance of organizing the data and how to achieve this using spreadsheet and SQL language. Next, you will also learn how to convert and format your data using SQL language. Later, you will see how to combine data from multiple database tables and perform data calculations using SQL and spreadsheets.

2.6. Share Data Through the Art of Visualization

Before you start making visualization of your data, you first learn the key concepts like design thinking that play an important role in data visualization. Also, you will start exploring Tableau for data visualization and make some simple visualization and learn how to develop presentations and slideshows.

2.7. Data Analysis with R Programming

Starting this section by discovering the R programming language that is used for data analysis and how to use its IDE called R studio. Next, you will start learning the concepts of the R language and how to use its functions and also apply these functions to data for analysis purposes. Later, you will gain some knowledge of data visualization using the R language.

2.8. Google Data Analytics Capstone

This last section will allow you to showcase your skills to your employee after completing this specialization by choosing an analytics-based scenario and asking questions about the problem you are trying to solve, preparing the data, analyzing them, and visualizing the final result.

Conclusion

Data analysis is one of the best skills to have if you will be a data scientist or even going to create your own company since this will help you understand your market size and however you are going to solve this problem.

Difference between == and === Equal Operator in JavaScript

In one of the recent JavaScript interview for a Java web development position, one of my readers was asked this questions, What is the difference between comparing variables in JavaScript using "==" and "===" operator? My reader got shocked because he was from Java background and doesn't have great exposure to JavaScript, though he was pretty much familiar with some JavaScript function, event handling, and some jQuery tricks, he wasn't aware of subtle details of JavaScript. He did the right think, politely said that he is not aware of the difference between == and === operator. Though It did not affect his interview performance much, he was keen to know about this as soon as he finished his interview. He asked to me as well, and that's the reason of this post.

How to use jQuery First time? HelloWorld Example

What is jQuery
jQuery is nothing but a JavaScript library that comes with rich functionalities. It's small and faster than many JavaScript codes written by an average web developer. By using jQuery we can write less code and do more things, it makes web developer's tasks very easy. In simple words, jQuery is a collection of several useful methods, which can be used to accomplish many common tasks in JavaScript. A couple of lines of jQuery code can do things that need too many JavaScript lines to accomplish. The true power of jQuery comes from its CSS-like selector, which allows it to select any element from DOM and modify, update or manipulate it.

When to use notify() and notifyAll() in Java

As a programmer, you must not rely on any particular selection algorithm or treatment of priorities, at least if you are trying to write a Java program that is platform-independent. For example, because you don't know what order threads in the wait set will be chosen for resurrection by the notify command, you should use notify (as opposed to notify all) only when you are absolutely certain there will only be one thread suspended in the wait set. If there is a chance more than one thread will be suspended in the wait set at any one time, you should probably use notify all.

Otherwise, on some Java virtual machine implementations, a particular thread may be stuck in the wait set for a very long time. If a notify always selects the most recent arrival from the wait set and the wait set always contains multiple threads, some threads that have been waiting the longest may never be resurrected.

2 Ways to test Exception in JUnit : Annotation vs try-catch

Error handling is a core part of coding but most of the time it just went under the radar when it comes to unit testing. How do we write a JUnit test that verifies that an exception is thrown? With the try-catch construct, of course, except that this time, the code throwing an exception is a good thing—the expected behavior. The approach shown in the below code is a common pattern for testing exception-throwing behavior with JUnit.

3 Best books to prepare OCAJP 7 (1Z0- 803) Exam - Java SE 7 Certification

Even though the latest OCAJP exam is OCAJP8, the OCAJP7 still the most popular one, at least from the email I receive, I can say that more readers ask for OCAJP7 recommendations and preparation tips than OCAJP8. I have always said the three golden rules of success in the OCAJP exam are selecting a good book, writing programs, and doing mock exams like Whizlabs or Enthuware practice tests. In this article, you will find some good OCAJP7 books to deal with the first part. For those, who are new to the structure of Java SE 7 certification, it's now divided into two parts, the OCAJP and OCPJP. The OCAJP stands for Oracle Certified Associate Java Programmer and it's an associate-level exam.

Top 10 WebSites to Learn Java Online for FREE

Top 10 Websites to Learn Java Online for FREE
-------------------------------------------
Programming Java for Beginners - The Ultimate Java Tutorial from Udemy http://codecondo.com/go/learnjava/
CodingBat - The Website for practicing Java Online http://codingbat.com/

Java Basics Tutorials from Oracle http://www.oracle.com/technetwork/topics/newtojava/overview/index.html
Introduction to Programming in Java - The book http://introcs.cs.princeton.edu/java/home/

Learn Java Online - Website to learn Java Interactive http://www.learnjavaonline.org/
Learn Java The Hard way - https://learnjavathehardway.org/
Programming By doing - http://programmingbydoing.com/

Java for Complete Beginners - The FREE Video Tutorial https://www.udemy.com/java-tutorial
Java Programming Tutorials for beginner - The newboston Video tutorial https://www.youtube.com/course?list=ECFE2CE09D83EE3E28

Object-Oriented Programming with Java - The University course http://mooc.cs.helsinki.fi/programming-part1/registration-and-how-get-started

10 Advanced Java Books for Experienced Developers

1) Effective Java
This is the first book every intermediate Java developer should read. It's not for beginners, and expert already knows most of the trick buts its absolutely critical for Java developer with a couple of years of experience. This book is your first step towards becoming an expert Java developer.

If you are working in Java for a couple of years and want to move from that advanced level, here are a couple of books to read.
-------------------------------------------

2) Java Concurrency in Practice

3) Java 9 Modularity

4) Definite guide of Java Performance by Scott Oaks

5) Head First Design Pattern

6) Test-Driven

7) Well-grounded Java Developer

8) Java NIO by

9) Java By Comparision

10) Refactoring

11) Modern Java in Action
This is the bonus book but how can you be a Java expert without knowing anything about Java 8 even after 1.5 years or its launch? So you must read this book to get a feel of new Java 8 features and motivation behind them.

Top 10 Java HashMap, Hashtable, ConcurrentHashMap Interview Question

Java HashMap, Hashtable, ConcurrentHashMap Interview Question
--------------------------------------------------------------
How to synchronize HashMap in Java?
How to sort HashMap in Java on values?
What is the difference between Hashtable and HashMap?
What is the difference between HashSet and HashMap
Difference between HashMap and ArrayList in Java?
What is the difference between HashMap and LinkedHashMap?
What is the difference between ConcurrentHashMap and HashMap?
How does get() method of HashMap works internally?
What are the different ways to iterate over each entry in HashMap?
How to loop over Map in Java?
How HashSet internally works in Java?
Difference between TreeMap and TreeSet in Java

Top 5 Microsoft SQL Server Books for DBAs and Developers

Top 5 Microsoft SQL SERVER Books for DBAs and Developers

SQL Server Execution Plans by Grant Fritchey
Learn the basics of capturing plans, how to interrupt
them in their various forms, graphical or XML, and then
how to use the information you find. Diagnose the most
common causes of poor query performance so you
can optimize your SQL queries and improve your
indexing strategy.

SQL Server Concurrency: Locking, Blocking
and Row Versioning
by Kalen Delaney
Your application can have world-class indexes and
queries, but they won’t help you if you can’t get your data
because another application has it locked. That’s why
every DBA and developer must understand SQL Server
concurrency, and how to troubleshoot any issues.

SQL Server Transaction Log Management
by Tony Davis and Gail Shaw
Tony Davis and Gail Shaw strive to offer just the right level
of detail so that every DBA can perform all of the most
important aspects of transaction log management.

Troubleshooting SQL Server: A Guide for the
Accidental DBA
by Jonathan Kehayias and Ted Krueger
Three SQL Server MVPs provide fascinating insight into
the most common SQL Server problems, why they occur,
and how they can be diagnosed using tools such as
Performance Monitor, Dynamic Management Views, and
server-side tracing performance, so you can optimize
your SQL queries and improve your indexing strategy.

Defensive Database Programming
by Alex Kuznetsov
The goal of defensive database programming is to
help you to produce resilient T-SQL code that robustly
and gracefully handles cases of unintended use,
and is resilient to common changes to the database
environment.

That's all about top 5 good Microsoft SQL SERVER books.

Further Learning

1. The Complete SQL Bootcamp (Udemy)
2. Complete SQL + Databases Bootcamp: Zero to Mastery (ZTM)
3. SQL for Data Science [Coursera]
4. Database Design Fundamentals for Software Engineers [Educative]
5. SQL QuickStart Guide (Book)

20 grep, egrep and fgrep command examples in UNIX/Linux

1) How to find all matching lines in a file in UNIX?

$ grep "good" dict.txt

2) How to exclude lines in a file, which matches patterns using the GREP command?

$ grep -v

2) How to count the number of matching lines in a file in Linux?

$ grep -c "good" dict.txt

3) How to perform case insensitive search for a keyword in a text file?

grep command support case insensitive search through grep -i option, where i stands for ignore case. This is quite useful if you are looking for strings like "error", "Error" and "ERROR" in a file. without case insensitive search you may not get the full picture if your developers are using different cases for the same keyword. Doing a case the insensitive search will give you the full idea.

4) How to display matched keywords as colored in grep output?

5) How to perform a recursive search using grep command in UNIX?

By using grep -R option, which performs a recursive search to sub-directories

6) How to make your grep command faster?

grep is very slow on UTF-8. Use “LANG=C grep …” to increase speed.

$ echo $LANG

en_US.UTF-8

$ time grep ‘^….’ /usr/share/dict/words >/dev/null

real 2m16.795s

user 2m10.536s

sys 0m0.087s

$ export LANG=C

$ time grep ‘^….’ /usr/share/dict/words >/dev/null

real 0m0.031s

user 0m0.028s

sys 0m0.003s

6) How to display lines above and below matching lines using grep command in Linux

grep support an option called --context

You have even option to display n number of lines after the match, or just show lines above and below of matching lines using -A and -B.

7)

How to learn more about grep command in Linux box itself, use the following commands :

man grep

info grep

8) How to search for a given string in multiple files in UNIX

how to print the name of all files which contains a particular String

9) How to use regular expression with grep command in UNIX.

You can use a basic set of regular expressions with grep command as shown below. There are two ways to use regular expression with grep command either by using grep -e option or grep --regex option

10) How to search for full words in a file in Linux using GREP

grep -w

11) How to display only the name of the files, which matches a given pattern?

Here we don't want matching lines to be printed, we only want to know the files, which contains matching lines.

grep -l option is our solution

12) How to show only the matched String

13) How to show the position of the match in the line

14) How to show numbers while display grep output

15) egrep command examples

16) fgrep command examples

That's all on this list of grep command examples in UNIX/Linux. We have learned a lot of good options of grep command, in fact, I would say Every Linux user must know these grep option to take full advantage of grep command in Linux. Let us know if you got any cool grep tips.

10 most useful command in VI Editor in Unix

1) finding form up "/" for ClOrdID , use n and shift n for navigation.
2) finding form bottom "?" looking for Execution Report 35=R
3) find and replace
Vi Replace Command

One other shortcut that might be worth mentioning is that 1,$ and % both indicate all the lines in the file. Therefore,

:1,$s/search_string/replacement_string/g
and

:%s/search_string/replacement_string/g

How to remove ^M from unix files using VI editor

1) ^M is DOS line break charater which shows up in unix files when uploaded from a windows file system in ascii format.
To remove this, open your file in vi editor and type
:%s/(ctrl-v)(ctrl-m)//g
and press Enter key.
Important!! - press (Ctrl-v) (Ctrl-m) combination to enter ^M character, dont use â€œ^â€ and M.
2) Your substitution command may catch more ^M then necessary. Your file may contain valid ^M in the middle of a line of code for example. Use the following command instead to remove only those at the very end of lines:
:%s/(ctrl-v)(ctrl-m)$//g

3) In some flavors of vi (e.g. RedHat), vi does it for you with:
:set fileformat=unix

4) the simplest way is to use the command dos2unix

5) If you wan to use space in file name the inclose the name in between quotes

''

4) Seeing command history in Vim
5) saving data and quiting
6) Inserting data
7) deleting data
8) cut copy past, pasting above line and below line
9) opening multiple file in VI and navigating between them
10) using ctrl+Z for suspending process
11) running bash commands from VI
12) Shortcut of keyboard also work in VI editor , like my favorite shortcut ctrl+w worked there.
Ctrl +R is act as Redo in VI editor.

VI mein agar yadi kisi directory ke name mein / hai aur wo aapko replace karna hai to usko escape kar do with \ e.g. \/ .
2.Abhijit told me how to open another rfile in VI and then navigate between that ^filename for opening the file and then :e #1 , :e #2 for navigating the file , we did this before by opening five files together while doing CST morning check and then using :n for navigating to next file.

Also for opening VI in readonly mode use the option â€œVI â€“R â€œ option.
In VIM we can use :help for getting help or :help fixdel for a specifc thing.
How to execute shell commands inside vi ?
!command , or select an ara using V/v and hit ! and then type the command and the selected area will lbe deleted ,fed into the command and replaced with the output of the command.

If we are doing something in VI and wanted to go shell without closing the vi then we can use command â€œ!shâ€ and go to the shell finish the work, do exit and comes back to vi. ! is used to execute shell commands from shell e..g !date.
â€¢ After doing ls â€“l abc.txt if you want to open abc.txt you can use vi !$ (last argument)

10 most useful VI shortcut
-----------------------------
CTRL + R -- Redo
yy -- yank
dd -- delete , 5dd
p and shift+P - Paste
5. how do you get visual block in VI , you can get the visual block by pressing ctrl+V and then use yy to copy the selcted block , it can be use to copy a region from VIM into the windows clipboard without using the mousse , V(move) + y or lower case v for sections of lines or Ctrl+v for blocks.
:e for opening a new file from inside VI
VI - R for opening a file in readonly mode.

Top 10 questiosn in Thread

-------------------------------------
One of my room mate have been preparing for java interview from past few days.
1) Since start() method of Thread class eventually calls run() method ? why should we not directly call run() method ?

2) I have two separate threads running separate task but I want them to run in a specic order ? how can I acheive this ?

3) What will happen if I call start() method on a running thread ?

4) What is the difference between sleep() and wait() method ?

5) What are the ways you can stop Thread ?

6) How do you find if a thread holds a lock or not ?

7) What is deadlock and how will you fix this ?

8) What is the difference between interuppted() and isInteruppted() ?

9) How do you acheive thread intercommunication ?

10) What is volatile modifier ?

Top 10 Courses for Java Developers on PluralSight

PluralSight is one of the best website to learn new technologies, particularly on Computer Science and Information Technology e.g. Programming langague, Framework, Library, Testing etc. I am a huge Pluralsight fan and have gone through a lot of courses there. here are some of my fav courses :

For Java :

1)Jim Wilson's course on Java Fundamentals.Even if you are a experienced java developer ,you would love these course & find something new.

2)Richard Warburton's Java Fundamentals: Collections

2)Understanding the Java Virtual Machine series.Advance course.

3)Unit Testing In Java With JUnit

4)Design patterns : Design Patterns Library

4)Concurrency :Applying Concurrency and Multi-threading to Common Java Patterns

5) Creating Your First Spring Boot Application Dan Bunker

6)Creating an Automated Testing Framework With Selenium

7)Spring Fundamentals

8)SOLID Principles of Object Oriented Design

9)Introduction to Spring MVC 4

11)Maven Fundamentals by Bryan Hansen

That's all about some of the best courses to learn Java. The list includes Java courses for beginners as well as for exprienced Java programmers. It has basic courses to learn Java fundamentals and Spring framework but also contains some advanced courses to learn unit testing, design patterns, Spring security, Concurrency, Spring MVC, Spring Boot etc.

Top 5 Machine Learning Algorithms for Data Science and ML Interviews

Hello guys, you may know that Machine Learning and Artificial Intelligence have become more and more important in this increasingly digital world. They are now providing a competitive edge to businesses like NetFlix's Movie recommendations. If you have just started in this field and are looking for what to learn, then I will share 5 essential Machine learning algorithms you can learn as a beginner. These necessary algorithms form the basis of most common Machine learning projects. Knowing them well will help you understand the project and model quickly and change them as per your need.

Difference between Random, ThreadLocalRandom and SecureRandom

There were used to be days when Math.random() method was the only way to generate random numbers in Java, but with the evolution of Java API, as of JDK 7, we now have 3 classes to generate Random numbers i.e. java.util.Random, ThreadLocalRandom, and SecureRandom. In this article, we will compare these three classes and learn some key differences between Random, ThreadLocalRandom, and SecureRandom in Java.

1. Java’s default Random class is expensive to initialize, but once initialized, it can be reused.
2. In multithreaded code, the ThreadLocalRandom class is preferred.
3. The SecureRandom class will show arbitrary, completely random performance. Performance tests on code using that class
must be carefully planned.

Random vs ThreadLocalRandom in Java

As the name suggests, the main difference between these two is how thread-safety is handled. The main operation is responsible for generating random number nextGaussian() of java.util.Random is synchronized. Since this method is used by all the methods which return random number, in multi-threading environment this method becomes a bottleneck.

In short, if two threads use the same random instance at the same time, one will have to wait for other to complete its operation. On the other hand, ThreadLocalRandom class uses a thread-local concept, where each thread has its own random number generator.

So in a contended environment, it's better to use ThreadLocalRandom. One more performance benefit of using this class is that it reuse an expensive-to-create object.

Difference between Random, ThreadLocalRandom, and SecureRandom in Java
As opposed to synchronization difference between ThreadLocalRandom and Random, SecureRandom is algorithmic different than Random and ThreadLocalRandom. Both Random and ThreadLocalRandom (later is sub-class of former) implements a typical pseudorandom algorithm. While these algorithms are quite sophisticated.

The difference between those classes and the SecureRandom class lies in the algorithm used. The Random class (and the ThreadLocalRandom class, via inheritance) implements a typical pseudorandom algorithm. While those algorithms are quite sophisticated, they are in the end deterministic. If the initial seed is known, it is easy to determine the exact series of numbers the engine will generate. That means hackers are able to look at series of numbers from a particular generator and (eventually) figure out what the next number will be. Although good pseudorandom number generators can emit a series of numbers that look really random (and that even fit probabilistic expectations of randomness), they are not truly random.

The SecureRandom class, on the other hand, uses a system interface to obtain random data. The way that data is generated is operating-system-specific, but in general, this

source provides data based on truly random events (such as when the mouse is moved).

This is known as entropy-based randomness and is much more secure for operations

that rely on random numbers.

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