IO Streams

The core Java language does not have any IO methods.
For a program to do IO, it must import an IO
package.
These notes (and most programs) use the package java.io.

Data for a program may come from several
sources.
Data created by a program
may be sent to several destinations.
The connection between a program and a data source
or destination is called a stream.
An input stream handles data
flowing into a program.
An output stream handles data
flowing out of a program.

In the picture, each “O” is a piece of data.
The data are streaming from the source into the program,
and streaming from the program to the destination.