声明扫描仪读取system.in

Question

Looking at Java tutorials, it seems you have to wrap up multiple layers of objects when declaring a scanner eg http://docs.oracle.com/javase/tutorial/essential/io/scanning.html

s = new Scanner(new BufferedReader(new FileReader("xanadu.txt")));

has both BufferedReader and FileReader . However, if I'm reading from System.in do I need to / is there any benefit to doing this? Do the two options behave differently?

Scanner s = new Scanner(new BufferedReader(new InputStreamReader(
            System.in)));

vs

Scanner s = new Scanner(System.in);

Answer 1

The buffering part is definitely different. Please read more about IO buffering here: http://docs.oracle.com/javase/tutorial/essential/io/buffers.html

Answer 2

Difference is in the efficiency. If used properly BufferedReader prevents bytes that are read from file to be converted into characters and then returned back. So using BufferedReader is recommended.

Additionally, you can specify buffer size, that is very handy.