Java is a computer programming language that is concurrent, class-based, object-oriented, and specifically designed to have as few implementation dependencies as possible. It is intended to let application developers “write once, run anywhere” (WORA), meaning that code that runs on one platform does not need to be recompiled to run on another. Java is, as of 2014, one of the most popular programming languages in use, particularly for client-server web applications.
Java was originally developed by James Gosling at Sun Microsystems (which has since merged into Oracle Corporation) and released in 1995 as a core component of Sun Microsystems’ Java platform. The language derives much of its syntax from C and C++, but it has fewer low-level facilities than either of them.
Java is used in several different ways. Java programs run on desktops and laptops on all of the major operating systems. Java applets are stored on a server, sent over the Internet, and automatically executed by a web browser. Applets are usually small helper applications, such as a currency converter used by an ordering system. On the other side of the client / server paradigm, Java servlets are small programs intended to run on a server rather than on a client computer. Java programs are found in small devices such as cable boxes, game consoles, and cell phones, with the Android implementation of the Java language being the most prevalent. The concepts covered here will give you a foundation to use Java in all these ways and more.