Seputar Ilmu

Java Generics Tutorial Generics in Java is one of important feature added in Java 5 along with Enum, autoboxing and varargs, to provide compile time type-safety. Generics is also considered to be one of the tough concepts to understand in Java and somewhat it�s true as well. I have read many articles on generics in Java, some of them are quite good and detailed but I still felt that those are either too much technical or exhaustively detailed, so I thought to write a simple yet informative article on Java generics to give a head start to beginners without bothering their head too much. In this Java generics tutorial, I will cover How Generics works in Java , some mysterious wildcards in Generics and some important points about Generic in Java. I will try explaining generics concept in simple words and simple examples. Read more �

From Java 5 onwards it's easy to left pad Integers with leading zeros when printing number as String. In fact, You can use the same technique to left and right pad Java String with any characters including zeros, space. Java 5 provides String format methods to display String in various format. By using format() method we can add leading zeros to any Integer or String number. By the way, this is also known as left padding Integers with zero in Java . For those who are not familiar with left and right padding of String, here is a quick recap; When we add characters like zero or space on left of a String, its known as left padding and when we do the same on the right side of String, it's known as right padding of String. This is useful when you are displaying currency amounts or numbers, which has fixed width, and you want to add leading zeros instead of space in front of Integers. Read more �

Printing array values in Java or values of array element in Java would have been much easier if arrays are allowed to directly prints its values whenever used inside System.out.println() or format and printf method , Similar to various classes in Java do this by overriding toString() method . Despite being an object, array in Java doesn't print any meaningful representation of its content when passed to System.out.println() or any other print methods. If you are using array in method argument or any other prominent place in code and actually interested in values of array then you don't have much choice than for loop until Java 1.4. Things has been changed since Java 5 because it introduced two extremely convenient methods for printing values of both primitive and object arrays in Java . Arrays.toString(array) and Arrays.deepToString(twoDimensionArray) can print values of any array. Main difference between Arrays.toString() and Arrays.deepToString is that deepToString i...

Static import in Java allows to import static members of class and use them, as they are declared in the same class. Static import is introduced in Java 5 along with other features like Generics , Enum , Autoboxing and Unboxing and variable argument methods . Many programmer think that using static import can reduce code size and allow you to freely use static field of external class without prefixing class name on that. For example without static import you will access static constant MAX_VALUE of Integer class as Integer.MAX_VALUE but by using static import you can import Integer.MAX_VALUE and refer it as MAX_VALUE . Similar to regular import statements, static import also allows wildcard * to import all static members of a class. In next section we will see Java program to demonstrate How to use static import statements to import static fields. Read more �

HashMap vs EnumMap in Java What is the difference between EnumMap and HashMap in Java is the latest Java collection interview question which has been asked to a couple of my friends? This is one of the tricky Java questions , especially if you are not very much familiar with EnumMap in Java , which is not uncommon, given you can use it with only Enum keys . The main difference between EnumMap and HashMap is that EnumMap is a specialized Map implementation exclusively for Enum as key. Using Enum as key allows doing some implementation level optimization for high performance which is generally not possible with other objects as key. We have seen a lot of interview questions on HashMap in our article How HashMap works in Java but what we missed there is this question which is recently asked to some of my friends. Unlike HashMap , EnumMap is not applicable for every case but it's best suited when you have Enum as key. We have already covered basics of EnumMap and some EnumMap exam...

Parameterized Generic class and method in Java Writing Generic parametrized class and method in Java is easy and should be used as much as possible. Generic in Java was introduced in version 1.5 along with Autoboxing , Enum , varargs and static import . Most of the new code development in Java uses type-safe Generic collection i.e. HashSet in place of HashSet but still Generic is underused in terms of writing own parametrized classes and method. I agree that most Java programmers has started using Generic while working with the Java collection framework but they are still not sure how Generic can allow you to write Template kind of classes which can work with any Type just like the parametrized ArrayList in Java which can store any Type of element. In the last couple of article about Generics we have seen How Generic works in Java and explored wild cards of Generic in Java and In this part of Java Generic example we will see How to write parametrized Generic Class and method...

What is CountDownLatch in Java CountDownLatch in Java is a kind of synchronizer which allows one Thread to wait for one or more Threads before starts processing. This is very crucial requirement and often needed in server side core Java application and having this functionality built-in as CountDownLatch greatly simplifies the development. CountDownLatch in Java is introduced on Java 5 along with other concurrent utilities like CyclicBarrier , Semaphore , ConcurrentHashMap and BlockingQueue in java.util.concurrent package. In this Java concurrency tutorial we will what is CountDownLatch in Java, How CountDownLatch works in Java, an example of CountDownLatch in Java and finally some worth noting points about this concurrent utility. You can also implement same functionality using wait and notify mechanism in Java but it requires lot of code and getting it write in first attempt is tricky, With CountDownLatch it can be done in just few lines. CountDownLatch also allows f...