Java Never Ends - Absolute Java - page 1085

Thread.sleep
Thread.sleep is a static method in the class Thread that pauses the thread that includes
the invocation. It pauses for the number of milliseconds (thousandths of a second) given as
an argument.
The method Thread.sleep may throw an InterruptedException , which is a checked
exception and so must be either caught in a catch block or declared in a throws clause.
The classes Thread and InterruptedException are both in the package java.lang ,
so neither requires any import statement.
Note that Thread.sleep can be invoked in an ordinary (single thread) program of the kind
we have seen before this chapter. It will insert a pause in the single thread of that program.
SYNTAX
Thread.sleep( Number_Of_Milliseconds );
EXAMPLE
try
{
Thread.sleep(100); //Pause of 1/10 of a second
}
catch (InterruptedException e)
{
System.out.println("Unexpected interrupt");
}

The getGraphics Method
The other new method in Display 19.1 is the getGraphics method, which is used in
the following line from the method fill :

getGraphics Graphics g = box.getGraphics();

The getGraphics method is almost self-explanatory. As we already noted
in Chapter 18, almost every item displayed on the screen (more precisely, every
JComponent ) has an associated Graphics object. The method getGraphics
is an accessor method that returns the associated Graphics object (of the calling
object for getGraphics )—in this case, the Graphics object associated with the panel
box. This gives us a Graphics object that can draw circles (or anything else) in the
panel box.
We still need to say a bit more about why the program in Display 19.1 makes you
wait before it will respond to the close-window button, but otherwise this concludes
our explanation of Display 19.1. The rest of the code consists of standard things we
have seen before.