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How to copy Files from one directory to other in Java

I have been programming in Java for a long time and you won't believe but there was no file copy method in the Java API until Java 7. At that time, our options were either write it ourself, using a FileInputStream, a FileOutputStream and a buffer to copy bytes from one to the other - or better yet, use the FileChannel.transferTo() method or just use the Apache Commons' FileUtils which was a life save those days and even today. JDK has evolved now and you have a decent API to copy files from one directory to another. In this article, I'll show you both the pre-Java code for copying files from one directory to other as well post Java 7 code which makes this task a lot easier.

Difference between int and Integer in Java?

Both int and Integer are two important data types in Java which often cause confusion between new Java developers. Both int and Integer used to represent numeric data and related to each other in the sense of primitive and Object. Int is a primitive data type that has 32-bit and stores values from  -2^31 to 2^31-1 while Integer is a class that wraps an int primitive inside it. In this article, you will learn why we need Integer Class in Java, particularly, if we already had the int data type, how to convert from int to Integer in Java, and various points on Integer in Java, ranging from basics to advanced BigInteger and AtomicInteger stuff.

Top 25 Examples of ConcurrentHashMap in Java 8 - Tutorial

The java.util.ConcurrentHashMap is one of the most important classes of JDK. It was introduced in JDK 1.5 along with other concurrent collection classes like CopyOnWriteArrayList and BlockingQueue. Ever since then, it has been a workhorse in concurrent Java applications. It won't be an exaggeration If I say there is hardly any concurrent Java application which has not used ConcurrentHashMap yet. The class was another implementation of Java .util.Map and a popular hash table data structure with concurrency inbuilt. This means you can also pass a ConcurrentHashMap to a method that is expecting a java.util.Map object. It was made scalable by dividing the whole map into a different segment, known as concurrency level, and then allowing threads to modify segments concurrently.

How to append text to file in Java? Example Tutorial

Hello guys, In this article, I'll teach you how to append text to a file in Java. Earlier, I have taught you guys how to create a file and write text into it, but, append is totally different than creating a new file and writing data into it. In the case of append, the file already exists and you just add text at the end of the file. One popular example of appending text into a file is a log file that is constantly updated because your application continuously appends log details into it. While you don't need to create a logging framework here, just knowing how to append text into an existing file in Java is useful for Java programmers of all kinds of experience.

What is the cost of Oracle Java Certifications - OCAJP8, OCPJP8, OCEWCD, OCMJEA?

One of the frequently asked questions about Oracle Java certifications, formerly known as Sun Certified Java programmer like OCAJP, OCPJP, OCEWCD, OCMEJA, etc. is about the cost of certification. Many of my readers often ask what the cost of OCAJP  like OCAJP 8 or OCAJP 11 and  OCPJP like OCPJP 8 and OCPJP 11 is? Is there any discount available? What are the fees of Java 8 certifications? How much Java architect exam cost? Etc. I have answered many of them one to one via Facebook and Email in the past, but after so many such requests, I decided to write a blog post about it.

Top 10 Object Oriented Programming Concepts and Fundamentals

Object-oriented programming (OOP) is a programming style that is used to solve the problem by thinking in terms of real-world objects like Car, Bag, Animal, etc. It also helps you to organize code, which makes it easier to understand and solve complex programs. Objects hold information about state and behavior. States are the characteristics of the object, or the words you would use to describe it, and usually, take the form of is or has descriptors. A computer is either on or off, a chair has four legs, and you have a name. Behaviors are the things the object can do, or the actions the purpose can perform and are usually verbs that end in ing, like You are sitting, using a computer, and reading this article.

40+ Java IO and Files Interview Questions with Answers

Good knowledge of Java IO API is important for any Java developer but many of them barely pay attention to Java IO and NIO API, and that's why they often struggle during Java interviews when a question related to Input-Output operation is asked. In the past, I have shared many Java interview questions on topics like Collections, Concurrency, JVM internals, Garbage Collection, OOP, Design Patterns and Data structure based coding problems, which received good feedback and helped many Java developer on their Java Interview preparation. Consequently, many of my readers were also asking about Java IO and File-based interview questions and this was one of the pending items on my TODO list for quite some time.

Top 50 Garbage Collection and Java Performance Interview Questions and Answers

Hello Java Developers, If you have gone through any Java Developer interview, particularly for senior developer role than you know that a good knowledge of JVM internals and Garbage collection is important. Even though Java and JVM take care of memory management for you, bad code can still cause memory leak and performance issues. For example, if you are creating millions of objects in a loop or keeping an un-intended reference of dead objects then you are putting additional strain on the Garbage collector and creating memory leak in your application. You cannot blame Java and JVM for that and the only way to avoid such errors is knowing about how Garbage collection works.

Top 3 Free Struts Books for Java EE developers - Learn Online, PDF download

Jakarta Struts is one of the most popular MVC frameworks to create a Java web application. Struts 1.0 had ruled the world in the early 2000 era before Spring MVC took over. Still, there are lots of projects written in Struts that need active maintenance, and that's why Struts developers are still in demand. It has not become anything like COBOL, but the latest version of Struts 2.0 is a capable web MVC framework with dependency injection and has a sizable community behind it. It has close competition with Spring MVC, but given the demand for Struts developer, it's still a good technology to learn if you are looking for a job in Java web development position.

Difference between CountDownLatch and CyclicBarrier in Java Concurrency

Difference between CountDownLatch and CyclicBarrier in Java
Both CyclicBarrier and CountDownLatch are used to implement a scenario where one Thread waits for one or more Thread to complete their job before starts processing but there is one difference between CountDownLatch and CyclicBarrierin Java which separates them apart and that is, you can not reuse same CountDownLatch instance once count reaches to zero and latch is open, on the other hand, CyclicBarrier can be reused by resetting Barrier, Once barrier is broken.