1.2 Java Workflow

Taking a program from a .java file into an executable has two main steps in Java: compilation and interpretation.

To run the code in Hello.java, we would first compile the code into a .class file using the command javac HelloWorld.java. Then, to run the code, we would use the command java HelloWorld.

In your terminal, the result would look like the following:

$ javac HelloWorld.java
$ java HelloWorld
Hello World!

Class Files

There are several reasons for the usage of .class files, which we will only cover briefly here. First of all, .class files are guaranteed to have been type-checked, making the distributed code safer. They are also more efficient to execute, and protect the actual source code in cases of intellectual property. We will not go into the details of .class files in this textbook beyond knowing that they are created after compilation.