Java Illuminated, 5th Edition

3.12 Using System.in and System.out

In order to print program output to the screen, we have been using statements like

System.out.println( "The value of b is " + b );

and

System.out.print( "Enter your first name > " );

And to instantiate a Scanner object, we used this statement:

Scanner scan = new Scanner( System.in );

It is now time to look at these statements in depth and understand them completely.

System is an existing Java class in the java.lang package. One of its fields is a static constant, out, which represents the Java console by default. Another of its fields is a static constant, in, which represents the keyboard by default. Because in and out are static, we refer to them using the class name, System, and the dot notation:

System ...