Installation, Compilation and Execution

You can find at https://spots.augusta.edu/caubert/teaching/general/java/prog.zip a simple java program, made of two files, Demo.java and Rectangle.java. You can also download them in a printable format.

To compile and execute them,

1. Install Java Development Kit (JDK). Hopefully the instructions at http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html should be clear enough. Using brew (for mac) or Chocolatey (for Windows) as package managers can make your installation easier.

2. Open a terminal and naviguate to the folder where you stored Demo.java and Rectangle.java.

3. To compile Rectangle.java using java compiler, type

   javac Rectangle.java

   in Linux/Unix-based systems, or (something like)

   "C:\Program Files (x86)\Java\jdk1.8.0_151\bin\javac" Rectangle.java

   in Windows. We will refer to those two commands as simply javac in the following: you can change the path and environment variables in Windows to make it more convenient to execute java compiler. A Rectangle.class file will be created, this program needs to be compiled before Demo.java, since this latter uses the class Rectangle. Once Rectangle is compiled, compile Demo.java, using

   javac Demo.java

4. To execute Demo.class, type

   java Demo

   You’ll be asked for your name and age. Just enter a string and hit the “enter” key, and then enter an integer and hit the “enter” key.

If you have questions, feel free to reach me at caubert@augusta.edu.

Presentation of the Programs

Those are really straightforward programs in java, hopefully allowing you to get familiar with this programming language. Start by reading Demo.java, the main purpose of those two files is to get some sense of the syntax, the overall construction will be very close to what you would do in any object-oriented programming-language.

Note that every java program

• has at least 1 class
• has only 1 public class
• has at most 1 method named main

and that java is case sensitive, every statement ends with ;.

One “feature” of java that often confuses programmers is that you need to “flush” the buffer after using a nextInt (or next"AnythingThatIsn'tLine" actually) to be able to read again from it. You can find it explained e.g. at https://stackoverflow.com/a/13102066.

Another “feature” that can be confusing to C# programmers is that Java does not provide an equivalent to int.TryParse “natively”. How to emulate such feature is discussed e.g. at https://stackoverflow.com/q/1486077/.

Pushing Further