Classpath in Java is not only used to load .class files, but also can be used to load resources e.g. properties file, images, icons, thumbnails, or any binary content. Java provides API to read these resources as InputStream or URL. Suppose, you have a properties file inside config folder of your project, and you want to load that properties file, how do you do that? Similarly, you have icons and thumbnails for your web applications on icons directory of your project, how do you load them? Answer is by using java.lang.Class' getResource() and getResourceAsStream() method. These method accepts path of resource as String and returns URL and InputStream respectively. You can obtain a reference of Class by calling either getClass() method or by using class literal. If you have an object, then you can call getClass() because its a non-static method, on the other hand, if you don't have any object, you can simply use .class with name of any class e.g. Sample.class will give you reference of java.lang.Class. These methods are available from JDK 1.1 and you can even use them anywhere you have access to core Java library. If you are creating J2ME games or application, you can use these method to load icons and tiles for your game, and all other resource for your application as well.
Java 8 now allows you to add non-abstract method implementations to interfaces by utilizing the default and static keyword. Methods with default keyword are known as default methods or defender methods in Java. Before Java 8, it was virtually impossible to change an interface once published. Any change e.g. addition of a new method would have broken all clients. That's why when Java 8 decided to switch to internal iterator implementation using forEach() method, they face a daunting challenge of breaking all implementation of Iterable interface. Since backward compatibility is top priority for Java engineers, and it wasn't practical to break all clients, they came up with idea of default method.
From long time one reason for me to update to newer Java version was always bug fix and performance improvement. Apart from major changes like Generics in Java 1.5 and Lambdas in Java 8, there are so many small improvements, performance optimization which just goes under radar, one of such change is creating empty ArrayList and HashMap with size zero in JDK 1.7.0_40 update. Many Java developer doesn't even know about these changes, part of the blame lies on Java developers like me, as I hardly read release notes of minor Java updates. Some times these changes are done as part of bug fixes and other time as minor optimization, but given popularity of ArrayList and HashMap in Java application impact of this simple Java optimization is huge.
TCP and UDP are two transport layer protocols, which are extensively used in internet for transmitting data between one host to another. Good knowledge of how TCP and UDP works is essential for any programmer. That's why difference between TCP and UDP is one of the most popular programming interview question. I have seen this question many times on various Java interviews , especially for server side Java developer positions. Since FIX (Financial Information Exchange) protocol is also a TCP based protocol, several investment banks, hedge funds, and exchange solution provider looks for Java developer with good knowledge of TCP and UDP. Writing fix engines and server side components for high speed electronic trading platforms needs capable developers with solid understanding of fundamentals including data structure, algorithms and networking.
An Armstrong number of three digits is an integer such that the sum of the cubes of its digits is equal to the number itself. For example, 153 is an Armstrong number, since 1**3 + 5**3 + 3**3 = 153, 371 is an Armstrong number since 3**3 + 7**3 + 1**3 = 371. Along with usual beginner exercises e.g. calculating factorial, reversing string or calculating prime numbers, this is a good exercise to build programming logic. It teaches you basic programming technique of how to use operator for something which is not obvious, for example, to solve this programming challenge, we first need to check if a number is Armstrong or not, and to do this we need individual digits of the number. how do we do that? well there is a programming technique, which you might have learned while doing number palindrome exercise.