JAVA ?

WHAT is JAVA ?

Java is a general purpose, high-level programming language developed by Sun Microsystems. The Java programming language was developed by a small team of engineers, known as the Green Team, who in

The Java language was originally called OAK, and at the time it was designed for handheld devices and set-top boxes. Oak was unsuccessful and in 1995 Sun changed the name to Java and modified the language to take advantage of the burgeoning World Wide Web.

itiated the language in 1991.

 

Java is an Object-Oriented Language

Java is defined as an object-oriented language similar to C++, but simplified to eliminate language features that cause common programming errors. The source code files (files with a .java extension) are compiled into a format called bytecode (files with a .class extension), which can then be executed by a Java interpreter. Compiled Java code can run on most computers because Java interpreters and runtime environments, known as Java Virtual Machines (VMs), exist for most operating systems, including UNIX, the Macintosh OS, and Windows. Bytecode can also be converted directly into machine language instructions by a just-in-time compiler (JIT). In 2007, most Java technologies were released under the GNU General Public License.

How java WORKS

Most of the other features of Java had previously existed in various other programming languages (but never all at once).  Most explanations of these advantages (e.g., distributed programming, multi-threading, security) are well beyond the scope of this course. However, there are two features that I will briefly address.

Another feature that was introduced with the Java language is the ability to write special Java programs (called applets) that are designed to run on the World Wide Web. You could write a Java applet and put the bytecode on a web page; if anyone with a Java-enabled web browser goes to your web page, that applet bytecode will be downloaded to the browsing computer and executed within the web browser. Of course, this would not be possible without platform independence. This feature had a major effect on the rapid proliferation of Java and many instructors (including myself) taught programming using applet-based programs. However, for a variety of reasons, I have decided to postpone a discussion of applets (and more generally, graphic user interfaces) to the end of the course.

Java is also one of the first languages to be "library-based" in that the designers of the language have included a large number of pre-existing programs. A programmer can connect their program to these general purpose programs as needed. It frees up the programmer's time since s/he doesn't have to write as much code. We'll start exploring this library called the API  (application programmer interface) after we learn a substantive amount of the Java language itself.

Java vs. C#

Microsoft's recent language, C# (a variation of  C/C++), was the first major language after Java to have a compile then link-execute cycle.  C# has also addressed most of the other issues that were Java advantages and C# has introduced other advantages as well. However, Microsoft does not seem to be interested in true platform independence (for example, there still is no C# bytecode interpreter for Linux). Also, sections of the C# software libraries require additional purchases beyond the basic cost of the language. 

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