Introduction to Java

1. Why Java?

   2017 Programming Language Ranking on IEEE Spectrum ranks Java #1 for jobs, and #2 overall (Python 100.0, Java 99.4). IEEE uses data from 10 different sources. You can create a custom ranking (change weights).

   Coding Dojo found Java #2 for number of job listings (SQL was ranked #1, but SQL isn’t a general programming language). Python moved to up #3 (40K postings), slightly ahead of Javascript.

2. About the Java language.

   Java is a compiled, statically typed programming language designed for object-oriented programming. All code is contained in classes. Java is very portable – compiled code can run on any computer with a JVM installed. See slides (below) for example of Java code.

3. How Java works.

   The Java compiler produces machine-independent byte code for a virtual machine. The Java virtual machine (JVM) verifies and runs the byte code. This means that after you compile a Java program, you can run it on any machine that has a JVM of the same version. Even the graphics are portable. You can write a Java program on Windows, compile it, and then run it on a Mac or Linux machine.

   The byte code (produced by compiler) is contained in .class files, which are usually packaged into JAR files (jar is just an archive of files in ZIP format, similar to a library). This is different from languages such as C or C#, where the code must be recompiled for each target platform.

Slide presentation: Intro-to-Java