Create HelloWorld.java

These 17 lines of text are comments. They are not part of the program;
 *  they serve to remind us about its properties. The first two lines tell
 *  us what to type to compile and test the program. The next line describes
 *  the purpose of the program. The next few lines give a sample execution
 *  of the program and the resulting output. We will always include such 
 *  lines in our programs and encourage you to do the same.