A constructor is a special dedicated method to initialize a new instance of a class. The constructor method for a class will have the same name as the class. A class can contain more than one constructor method, but each having a different set of parameters. They are called overloaded constructor methods. A constructor method is the first method that’s called and executed when a new object is instantiated. It’s primary usage is to assign default values to variables, do basic cleanup or calculation, etc. A constructor method is not Read More

A Java object is basically a set of data, data structures, and methods combined together to form a single entity. An object is an instance of class. Therefore, a class is said to be a blueprint of an object. Every object instantiated from a class will contain its own copy of member variables and member methods (unless they are declared static). Member methods are created to help an object process its member variable and take required actions. Creating Objects The are three major steps involved while creating an object from Read More

JDK is an abbreviation for Java Development Kit. The JDK product, formerly owned by Sun Microsystems, is now owned and maintained by the  Oracle Corporation. JDK is licensed under the GNU General Public License (GPL). That is, JDK is a free to use software package. It is a comprehensive development environment primarily aimed for Java developers. It basically envelops a run-time environment that is stacked on top of a operating system. Other tools needed by a Java progammer to code, compile, debug, and test programs also integrate well with the JDK Read More

CLASSPATH is an environment variable which tells the Java compiler and the JVM where to look for Java class files. In Java 1.2 and later, the CLASSPATH variable is less critical because Java knows how to find the default classes and because Java loads classes from the current directory by default. If you do not want to use an environment variable, you can use the -classpath argument to the Java compiler or the JVM as such: javac -classpath . JavaProg To add a jar file to your CLASSPATH, include the Read More

The JRE is the Java Runtime Environment. The JRE consists of the Java Virtual Machine, the Java libraries, and all other components necessary to run Java applications and applets. Sun distributes the JRE seperately, or as part of J2EE, J2SE, and J2ME.          

A Java package is a set of classes which are grouped together. This grouping helps to organize Java classes and codevent multiple Java classes with the same name. Using Java Packages To use a package in your Java source code, you must either import the package or use the fully qualified class name each time you use a class. Using Fully Qualified Class Names This example uses the Ammunition class from the ballistics package: ballistics.Ammunition caliber = new ballistics.Ammunition(); As you can imagine, using fully qualified class names can become Read More

JNI is the Java Native Interface. JNI is an interface between Java and applications and libraries written in other languages. As an example, JNI enables Java programs to use C libraries and also enables C programs to use Java classes. JNI is distributed as part of the JDK.          

J2EE is Java 2 Enterprise Edition. J2EE is Sun’s preferred Java platform for multi-tier enterprise applications. J2EE enhances J2SE with: Enterprise JavaBeans components Java Servlets API JavaServer Pages XML For more information on J2EE, visit J2EE.

A Java class is a group of Java methods and variables. Each Java source code file can contain one public class. The name of this public class must match the name of the Java source code file. If the public class is called “ballistics,” then the filename would be “ballistics.java.” Example Java Class class Ammunition { int diameter; int length; String name; } Java Superclass A Java superclass is a class which gives a method or methods to a Java subclass. A Java class may be either a subclass, a Read More

Java is a free-to-download programming language that is utilized in a variety of programs, such as computer games and 3D mapping technology. It can also be used to create small programs, called “applets,” that can be embedded in web pages. If you’re looking to install Java on your Linux-based computer, you have several options: First, download the latest version of Java: http://www.oracle.com/technetwork/java/javase/downloads/index.html Manual Non-RPM method This method does not required administration rights and allows you to install multiple versions of Java on the same computer After downloading Java, switch to Read More