Difference between Period and Duration class in Java 8? [Example]

What is the difference between Period and Duration class in Java is one of the popular Java 8 interview questions and has been asked too many of my readers recently. If you were also wondering the difference between Period vs Duration and when to use Period over Duration and vice-versa then you have come to the right place. Java 8 has two classes to represent differences in time like Duration and Period. The main difference between Period and Duration is that they represent the difference in different units, A Duration is used to calculate time difference using time-based values (seconds, millisecond, or hours) but Period is used to measure the amount of time in date-based values like days, months and year.

What is Double Brace Initialization in Java? Example Initializing HashMap and List with values in Java

Double brace initialization is a Java idiom to initialize a Collection like a list, set, and map at the time of declaration. At times, you need a list of fixed elements e.g. supported products, supported currencies, or some other config, and on-the-spot initialization reduces the line of code and improves readability. Double brace initialization idiom becomes popular because there is no standard way to create and initialize Collection at the same time in Java. Unfortunately, unlike other JVM languages like Scala and Groovy, Java doesn't support collection literals yet. 

Right way to Close InputStream and OutputStream in Java - Example

For some unknown reasons many Java programmers are not very comfortable with IO package. I don't know why, but I have found them much more comfortable with java.lang and java.util than java.io. One possible reason of this could be that, writing IO code require a bit of C++ like programming, which involves doing clean-up, releasing resources once done etc. Since Java made coding a lot easier by taking care of memory management, unknowingly it also introduced bad practice of not releasing resource after use like database connections, socket connection, files, directory, printers, scanners or any other scarce resource.

How to implement Command Design Pattern in Java with Example

Hello guys, it's been a long since I have shared a Java design pattern tutorial. I did share some courses to learn design patterns but haven't really talked about a particular design pattern in depth. So, today, we'll learn one of the important design pattern, which is often overlooked by Java developers. Yes, I am talking about the Command Pattern which can help you write flexible, loosely coupled code for implementing actions and events in your application. In simple words, the command design pattern is used to separate a request for action from the object which actually performs the action. This decoupling between Invoker and Receiver objects provides a uniform way to perform different types of actions. This decoupling is achieved using a Command object, which is usually an interface with methods like execute(). 

Can a Non Static Method Access a Static Variable/Method in Java?

"Can a non-static method access a static variable or call a static method" is one of the frequently asked questions on the static modifier in Java, the answer is, Yes, a non-static method can access a static variable or call a static method in Java. There is no problem with that because of static members i.e. both static variable and static methods belong to a class and can be called from anywhere, depending upon their access modifier. For example, if a static variable is private then it can only be accessed from the class itself, but you can access a public static variable from anywhere.

How to create Tabs UI using HTML, CSS, jQuery, JSP and JavaScript? Example

JSP is still a popular technology for developing view part of Struts and Spring-based Java applications, but unfortunately, it doesn't have rich UI support available in GWT, or any other library. On another day, we had a requirement to display HTML tables inside tabs, basically, we had two tables of different data set and we need to display them in their own tabs. Users can navigate from one tab to another, and CSS should take care of which tab is currently selected, by highlighting the active tab. Like many Java developers, our hands-on HTML, CSS, and JavaScript are a little bit tight than a web guy, and since our application is not using any UI framework, we had to rely on JSP to do this job.

How to use Adapter Design Pattern in Java with Example

The adapter design pattern in Java, also known as the Wrapper pattern is another very useful GOF pattern, which helps to bridge the gap between two classes in Java. As per the list of Gang of Four patterns, the Adapter is a structural pattern, much like Proxy, Flyweight, Facade, and Decorator patterns in Java. As the name suggests, the Adapter allows two classes of a different interface to work together, without changing any code on either side. You can view the Adapter pattern as a central piece of the puzzle, which joins two pieces, which can not be directly joined because of different interfaces.

java.lang.UnsatisfiedLinkError: no dll in java.library.path - Cause and Solution

"Exception in thread "main" java.lang.UnsatisfiedLinkError: no dll in java.library.path" is one of the frustrating errors you will get if your application is using native libraries like the DLL in Windows or .SO files in Linux. Java loads native libraries at runtime from either PATH environment variable or location specified by java.library.path system property depending upon whether your Java program is using System.load() or java.lang.System.loadLibarray() method to load native libraries. If Java doesn't find them due to any reason it throws "java.lang.UnsatisfiedLinkError: no dll in java.library.path". 

Spring Boot Error - Error creating a bean with name 'dataSource' defined in class path resource DataSourceAutoConfiguration

Hello guys, If you are using Spring Boot and getting errors like "Cannot determine embedded database driver class for database type NONE" or "Error creating a bean with name 'dataSource' defined in class path resource ataSourceAutoConfiguration" then you have come to the right place. In this article, we'll examine different scenarios on which this Spring Boot error comes and what you can do to solve them. The general reason for this error is Spring Boot's auto-configuration, which is trying to automatically configure a DataSource for you but doesn't have enough information. It is automatically trying to create an instance of DataSourceAutoConfiguration bean and it's failing.

Difference between WHERE vs HAVING clause in SQL - GROUP BY Comparison with Example

What is the difference between WHERE and  HAVING clause in SQL is one of the most popular questions asked on SQL and database interviews, especially to beginners? Since programming jobs, required more than one skill, it’s quite common to see a couple of SQL Interview questions in Java and .NET interviews. By the way unlike any other question, not many Java programmers or dot net developers, who are supposed to have knowledge of basic SQL, fail to answer this question. Though almost half of the programmer says that WHERE is used in any SELECT query, while HAVING clause is only used in SELECT queries, which contains aggregate function or group by clause, which is correct.

How to Set Classpath for Java on Windows and Linux? Steps and Example

What is CLASSPATH in Java? Classpath in Java is the path to the directory or list of the directory which is used by ClassLoaders to find and load classes in the Java program. Classpath can be specified using CLASSPATH environment variable which is case insensitive, -cp or -classpath command-line option or Class-Path attribute in manifest.mf file inside the JAR file in Java.  In this Java tutorial, we will learn What is Classpath in Java, how Java resolves classpath and how Classpath works in Java alongside How to set the classpath for Java in Windows and UNIX environment. 

Difference between Direct, Non Direct and Mapped ByteBuffer in Java?

ByteBuffer is one of the important classes of Java NIO API. It was introduced in java.nio package on JDK 1.4, it not only allows you to operate on heap byte arrays but also with direct memory, which resides outside the JVM. There are mainly three types of ByteBuffer in Java - Direct Byte Buffer, Non-Direct ByteBuffer, and mapped byte buffers. You can create both direct and non-direct buffers using java.nio.ByteBuffer class, while MappedByteBuffer is a subclass of ByteBuffer, which is created by FileChannel.map() method, to operate on memory-mapped file. 

String vs StringBuffer vs StringBuilder in Java? Example

Difference between String, StringBuffer, and StringBuilder

The String is one of the most important classes in Java and anyone who starts with Java programming uses String to print something on the console by using famous System.out.println() statements. Many Java beginners are not aware that String is immutable and final in Java and every modification in String creates a new String object. For example, when you get the substring, you get a new String, when you convert uppercase String to lowercase, a new String is created. Even when you remove space by calling the trim() method, a new String is returned. 

Java 8 forEach() Loop Example

Java 8 has introduced a new way to loop over a List or Collection, by using the forEach() method of the new Stream class. You can iterate over any Collection like List, Set, or Map by converting them into a java.util.sttream.Stream instance and then calling the forEach() method. This method performs given operation on every element of Stream, which can be either simply printing it or doing something else. Since stream can be sequential or parallel, the behavior of if this method is not deterministic if used with a parallel stream. 

Difference between Transient, Persistent, and Detached Objects in Hibernate

In the Hibernate framework, an entity can be in three states, transient, persistent, and detached. When an object is in a transient state, it is commonly referred to as a transient object, similarly, if it is in persistence and detached state, it is known as a persistent and detached object. When an entity is first created using the new operator like new User() and not associated with Hibernate session like you haven't called session.save(user) method then it is known as a transient object. At this stage, Hibernate doesn't know anything about this object and the object doesn't have any representation in the database like a corresponding row in the User table.