How to Iterate Over Rows and Cells of Excel file in Java - Example

Sometimes, you'd like to just iterate over all the rows in a sheet, or all the cells in a row. This is possible with a simple for loop.  Luckily, this is very easy. Row defines a CellIterator inner class to handle iterating over the cells (get one with a call to row.cellIterator(), and Sheet provides a rowIterator() method to give an iterator over all the rows. 

10 Free Courses to Learn System Design and Software Design in 2022 - Best of Lot

Hello guys, if you are preparing for System Design Interview or just want to improve your Software design skills and looking for best free resources like tutorials and free online courses then you have come to the right place. In the past, I have shared best System design courses, books, websites, and popular System design questions but a lot of you asked for free resources and that's why I am going to share best free System design courses I found online. These online courses are completely free and provides a diverse knowledge about different System design concepts and process. They are also created by experienced trainers and teacher who has gone through the same process and available on trusted online platforms like Udemy and YouTube. You can join one or more of these free System design courses to not only improve your Software design skill but also to prepare for your next System Design Interview. 

Top 5 Websites to Learn System Design and Software Design in 2022

Hello guys, if you are preparing for System design Interview and looking for best resources to master Software design and System design then you have come to the right place. Earlier, I have shred best System Courses, Books, and System Interview Questions and in this article, I am going to share best places to learn System design in 2022. Before we get to the best websites that will teach you everything you need to know about system design, let me tell you a little bit about what it really is. Systems design is basically the process of defining elements of a system including modules, architecture, components, interface, and data for a system based on a specific set of requirements. It can also refer to the process of defining, developing, and designing systems. These designs have to satisfy the specific needs of a company or an organization.

How to Learn Kubernetes, AWS, Azure, and Google Cloud using Whizlabs Hands-on Labs ?

Hello guys, Cloud computing is rapidly becoming one of the essential skill for all kind of developers and no matter what you will need to learn Cloud Computing if you want to remain marketable. I learned this truth couple of years ago and since then spent a lot of time learning AWS, Azure, Kubernetes, Docker, and Google Cloud Platform. The big problem with learning Cloud computing and different cloud platform like AWS and Azure is that you cannot learn them by reading books or watching course. You need real, hands-on practice which can only be possible by either using the free tier of respective platform or using hands-on labs like the one provided by Whizlabs and QwikLabs.  In this article, I am going to review Whizlab's comprehensive offering of hands-on labs to learn Cloud related technologies like Kubernetes, AWS, Azure, Openshift, Google Cloud Platform and Snowflake better.

Difference between Checked vs Unchecked Exception in Java? Example

Checked and Unchecked Exception is two types of Exception exist in Java. Though there is no difference in functionality and you can very achieve the same thing with either checked Exception or Unchecked Exception, there is some difference on exception handling part. In this Java tutorial we will see what is checked and Unchecked Exception in Java, Examples of Checked and Unchecked Exception and most importantly we will learn when to use Checked Exception and when to use Unchecked Exception in Java and lastly we will see the difference between checked and unchecked exception to understand things better. 

[Solved] How to solve java.lang.UnsatisfiedLinkError: no ocijdbc11 in Java with Oracle 11g, 12c, 19c and 21c

"java.lang.unsatisfiedlinkerror no ocijdbc11 in java.library.path" error comes when you try to connect to Oracle 11g database using OCI (thick) driver by using tns name, but the ocijdbc11.dll file is not available in PATH or java.library.path environment variable. ocijdbc11.dll is a native library and if you know Java searches native library in PATH or a location specified by java.library.path system property, if it doesn't find the dll, then it throws java.lang.unsatisfiedlinkerror no ocijdbc11 in java.library.path error. This dll is usually found in C:\Programs\Oracle\ora11g\bin\ocijdbc11.dll, but it could vary depending upon your Oracle installation.

How to deal with NullPointerException in Java with Examples - java.lang.NullPointerException Guide

The java.lang.NullPointerException or NullPointerException in Java is probably the first error or exception you will face in Java. It is a true nightmare for beginners in Java but pretty easy to solve once you get familiar with Exception handling in Java. What makes NullPointerException a little bit tricky to solve is its name which has a pointer in itself and Java does not support pointers like C++ or C, just like you don't have multiple inheritances in Java. As a Java developer with 20 years of experience, I have solved countless amount of NullPointerException and now I have developed a coding and debugging sense through which I can spot what causing a particular NullPointerException and how to fix it. 

How to use @EnableTransactionManagement in Spring Framework and Spring Boot? Example Tutorial

Spring Boot has a lot many annotations within its framework that a person can use. If you are searching for one, you have come to the right place. Needless to say, these annotations are essential for building a Spring Boot web application. Today we will look at an annotation that is widely used for transaction management in spring. So, what's the wait?! Let's start! But, before jumping into the sea of spring, let's first understand what a transaction means in spring and what it signifies. A transaction is used in Spring JPA which communicates to the database. we all know what a transaction represents on a database level. If not, no worries! let us all recall.

How to Fix 'javac' is not recognized as an internal or external command in Windows and Linux? Example

Hello guys, if you are trying to compile your Java source file and getting "'javac' is not recognized as an internal or external command" in Windows or Linux machine like Windows 10 or Redhat 8 but not sure what to do then you have come to the right place. This is a common Java related error and can occur to an operating system like Windows, Mac or Linux if java is not installed properly like only JRE is installed and JDK is not installed or javac is not added on PATH environment variable. In this article, I will explain what this error is and how you can fix it by following step by step guide I share, but if you still cannot solve this problem on your own then just ask for help in comments. But don't forget to check your PATH environment variable because that's where JDK/bin directory needs to be present, which contains all Java related commands including "javac" and "java" which are used to compile and run Java applications.

[Solved] How to fix VirtualBox - /sbin/mount.vboxsf: mounting failed with the error: Protocol error

Virtual box is a great tool for Java developer to run Docker and Linux on Windows Machine, especiall for them who need to develop and debug Java program in Linux environment. I use Oracle's virtual machine, VirtualBox to run the Linux operating system from my Windows machine. It's the most simple way to have two operating systems on your laptop or PC. Since I run most of the Java programs in Linux, VirtualBox gives me a nice interface to run UNIX commands right from the Windows box. This blog post is about the mounting of a shared folder failed error in Oracle's Virtualbox VM. It was working fine the day before yesterday and now, after I restarted my virtual box and tried to mount my shared folder, I was greeted by this error: "/sbin/mount.vboxsf: mounting failed with the error: Protocol error". 

How to fix java.lang.UnsupportedClassVersionError: Bad version number in .class files? Example

How to fix Bad version number in the .class file

"java.lang.UnsupportedClassVersionError: Bad version number in .class file" is a common error in Java programming language which comes when you try to run a Java class file which was compiled by different version of Java compiler than then JRE version you are using to run it. In our last article, we discussed that how to resolve Java.lang.UnSupportedClassVersionError and found that it comes when a major and minor version of the class is not supported by Java virtual machine or JRE running the program. Though "java.lang.UnsupportedClassVersionError: Bad version number in .class file" is a little different than that of its manifestation and Cause, both are related to the mismatch in compiler javac and runtime java version. 

How to Fix Must Override a Superclass Method Error Eclipse IDE Java | @Override annotation with interface methods

One of the annoying error while overriding Java method in Eclipse IDE is must override a superclass method error, This error is quite frequent when importing Java projects and after so long, still I haven't seen any permanent solution to it. Must override a superclass method the error comes in Eclipse if you have Java Class that implements interface and overrides a method from interface and uses @Override annotation. Unfortunately, Eclipse defaults to Java 1.5, which only recognize @Override annotation for the overriding method from the superclass and not from the interface.

How to fix "No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK" in Eclipse & Maven?

If you are like many Java developer who uses Maven and Eclipse to build Java project using M2Eclipse plugin, you might have seen this error before. I ran into it recently when I ran the Maven Install command for one of the Java projects, configured as Maven project,  only to realize that Maven builds failed after throwing this error. The main reason for this error is that Maven is not able to find javac (the Java compiler) which is required to compile Java source files. If you remember, the javac command comes in the bin directory of JDK, hence, you need a JDK installation in your local machine to compile the Java project.

How to fix java.sql.SQLException: Invalid column index? Example

"java.sql.SQLException: Invalid column index" is a frequent error while working in Java Database Connectivity (JDBC). As the name suggests "Invalid column index" its related to accessing or setting column in your SQL Query using prepared statement in Java. I have seen "java.sql.SQLException: Invalid column index" coming mostly due to two reason:

1) Setting column data using setXXXX(int coloumIndex) e.g. setInt(0) setString(0)

2) Getting column data using getXXX(int columnIndex) e.g. getInt(0) getString(0)

The most common cause of "java.sql.SQLException: Invalid column index" is a misconception that column index started with "0" like array or String index but that's not true instead column index starts with "1" so whenever you try to get or Set column data with column index "0" you will get "java.sql.SQLException: Invalid column index".

FIX Session is not connecting how to diagnose it? Example Tutorial

In this blog post of the FIX protocol tutorial series I would like to share my experience with connectivity issues around Fix Engines. to exchange messages or say to trade electronically clients connect to the broker using FIX protocol and for that, they use FIX Engine. In FIX protocol connection between two FIX Engines is refereed as FIX Session and we normally say whether FIX Session is connected or not connected. FIX Session normally has their start time, end time, and EOD time (End of day time) also called TradingSession start time, Trading Session End Time, and Trading Session EOD time.

How to fix java.lang.ClassNotFoundException: com.sun.jersey.spi.container.servlet.ServletContainer? [Solution]

The error message clearly says that the Java runtime is not able to find a class called ServletContainer for the Jersey library. This is the Servlet class you have specified in the deployment descriptor of your application. It's similar to DispatcherServlet of Spring MVC and this error is similar to the error you get when DisplayServlet was not in the classpath.
Anyway, java.lang.ClassNotFoundException: com.sun.jersey.spi.container.servlet.ServletContainer comes when you are trying to use Jersey but have not added required dependency on your classpath e.g. those JAR files which contain the class "com.sun.jersey.spi.container.servlet.ServletContainer".

How to Fix java.net.SocketException: Failed to read from SocketChannel: Connection reset by peer? Example

You might have seen the java.net.SocketException: Failed to read from SocketChannel: Connection reset by peer error while working with Java NIO based server which is using SocketChannel instead of InputStream for reading data from the network. In general, this can come at both client and server end of a client-server Java application which is using TCP/IP to connect each other. Though this exception usually comes at the server end and the client was complaining that they are not able to connect. 

How to Fix java.lang.OutOfMemoryError: GC overhead limit exceeded Error in JVM [Solution]

Hello guys, if you are getting  java.lang.OutOfMemoryError: GC overhead limit exceeded Error in your Java application and wondering how to solve this then read on. As suggested by Java virtual machine, java.lang.OutOfMemoryError: GC overhead limit exceeded error comes when JVM breached GG overhead limit; which means your application is spending too much of garbage collection time without freeing any meaningful space. Currently Java's HotSpot virtual machine throws "java.lang.OutOfMemoryError: GC overhead limit exceeded" when 98% of total time is spent in the garbage collection and less than 2% of heap memory is recovered. Now let's find out what are symptoms of this error? Before this out of memory error comes you will see very slow or hung Java application with high CPU usage, because your application is only doing GC. 

16 Essential Java ArrayList Examples for Beginners - Tutorial

Most of the Java interview questions on ArrayList asked freshers or Java developers with 1 to 2 years experience is just simply how to do tasks like how to sort ArrayList in Java, How to sort ArrayList in ascending and descending order, how to sort ArrayList on reverse order, how to search elements, how to remove an element using iterator etc. Since, I have written lots of Java tutorials on ArrayList, covering many general-purpose tasks like how to create an object of ArrayList and initialize to how to sort ArrayList in ascending and descending order, etc. 

How to empty an ArrayList in Java? clear() vs removeAll() method Example Tutorial

Many times we want to reset an ArrayList for the reusing purpose, by resetting we mean clearing it or removing all elements. There are two ways to reset an ArrayList in Java, by using the clear() method or calling removeAll(). If your ArrayList is small enough like it contains only 10 or 100 elements then you can use any of these two methods without worrying too much, but, if you have a huge list of lots of objects like an ArrayList containing 10M entries, then the choice of clear() vs removeAll() can make a huge difference in the performance of your Java application.

How to loop or Iterate over ArrayList in Java? Iterator, ListItreator, for loop and Enhanced foreach example

Looping ArrayList in Java or Iteration over ArrayList is very similar to a looping Map in Java. In order to loop ArrayList in Java, we can use either foreach loop, simple for loop, or Java Iterator from ArrayList. We have already touched iterating ArrayList in 10 Example of ArrayList in Java and we will see here in detail. We are going to see examples of all three approaches in this ArrayList tutorial and find out which one is clean and the best method of looping ArrayList in Java. Before start writing an example for loop in ArrayList let's think about why do we need to iterate, traverse or loop an ArrayList if it’s based on the index and backed by Array.

Top 20 Kotlin Interview Questions with Answers for Beginners and Experienced

Hello guys, if you are preparing for Kotlin Developer Job interview and looking for frequently asked Kotlin interview questions then you have come to the right place. In the past, I have shared Core Java questions, Scala interview questions as well as Groovy Questions and in this article, I am going to cover common Kotlin questions from interviews. In last a couple of years Kotlin has emerged from the shadow of Java and demand for Kotlin is increasing day by day. Google's decision to accept Kotlin as the official programming language for Android development triggered this rise and now Kotlin is also viewed as preferred backend development language, a shock for Java and Scala but its true. 

Coursera Review - Is the Meta Frontend and Backend Developer Certificates Worth It?

Hello guys, if you want to become a frontend or backend developer in 2022 and looking for a well structured, reputed, and completely online program then Meta's Frontend and Backend developer certificates on Coursera are great place to start with. The Certifications will come from Meta, parent company of Facebook (similar to how the Certificates come from Google in the Google Professional Certificates) and they are taught by expert Software engineers of Meta. This means you will not only learn the latest tech skills which are highly looked after by employers but also you will get a chance to learn from best people in the world. But, what separate this professional certificate on Coursera form others is the access to Meta Job board. 

Difference between a List and Array in Java? ArrayList vs Array Example

Hello there, if you are wondering what is the difference between a list and an array, or particularly an ArrayList and an Array in Java then you have come to the right place. Earlier, I have shared the best data structure and algorithm courses and in this article, I will explain to you the differences and similarities between a list and an array in Java.  Both array and ArrayList are two important data structures in Java and frequently used in Java programs. Even though ArrayList is internally backed by an array, knowing the difference between an array and an ArrayList in Java is critical for becoming a good Java developer. If you know the similarity and differences, you can judiciously decide when to use an array over an ArrayList or vice-versa. 

Top 20 JSON Interview Questions with Answers for Beginners and Experienced Developers

Hello guys, if you are doing for a web developer interview or a Java web developer interview where you need to write server side application or backend code which uses HTTP to send and receive data then you should prepare about JSON. It's one of the most popular way to exchange data between two systems or between frontend and backend, client and server and most of the top programming language has API to create and parse JSON like Java has Jackson and JavaScript can by default support JSON because its nothing but JavaScript Object Notation.  JSON is also the default data format for REST API  and even GraphQL uses JSON to send request and receive response.