Between the Braces

All of our small Java programs will look something like this:

class Hello
{

}

Everything that a program can do will be described inside the first brace and the final, matching brace of a class. To start with, there will be only one class per source code file, but in later chapters there may be several classes per source code file. The example program writes "Hello World!" to the monitor.

class Hello
{
  public static void main ( String[] args )
  {
    System.out.println("Hello World!");
  }
}

This looks like a lot of lines for doing such a little task. Usually programs have many more lines and the lines you see here help to keep them organized. The line

  public static void main ( String[] args )

shows where the program will start running. The word main means that this is the main method --- where the Java virtual machine will start running the bytecode version of the program. The main method of this program consists of a single statement:

    System.out.println("Hello World!");

This statement writes the characters inside the quotation marks to the monitor of the computer system.