I did not find any discussion on this question here in the community so I decided to create this topic. There is a well-told question among beginners in the Java language when it comes to data manipulation.
System.out is the default output of the system you are using. System.err is the default output of system errors. In a normal console application, both are likely to run on the console. But you can reconfigure the outputs to, for example, make the errors print in a text file, and leave the System.out printable on the screen.
System.in is the system input pattern, of type InputStream . It is already open, and ready to receive data. Typically, it matches the keyboard or any specified data source either by the environment, or by the users.
System.in - > You receive data
System.out and System.err - > They do data output. Can be reconfigured to write in different places
Default entry of type InputStream , usually connected to the keyboard in terminal / console-oriented programs.
Standard output of type PrintStream . Usually sends the data recorded on it to the console / terminal. Much used by console-based programs such as command line tools ( grep , find ).
Error output of type PrintStream . It works like System.out, except it is used to send error messages.
In a terminal-oriented Java application, both outputs will be the same (the command line), but you can reconfigure them so that Sistem.out continues to print to the terminal, and System.err writes to a file, for example.
This reconfiguration can be done directly on the terminal as these examples.
