Using predefined streams should include java.lang's three predefined stream variables: System.in, System.out, and System.err (defined as public and static and used by any part of program without reference to a specific System object). Terms are defined as follows:
- System.out (object of type PrintStream)
- Refers to standard output stream
- By default, this is the console.
- System.in (an object of type InputStream)
- Refers to standard input
- By default, this is the keyboard.
- System.err (object of type PrintStream)
- Refers to standard error stream
- By default, this is the console.