Understanding Java superclass hierarchy through System objects and methods

Question

I wanted to see if I can manipulate datastreams manually rather than relying on classes.
I knew that System.in was an InputStream object so it must use the said methods such as System.in.read()
I made a program for it. It gave me an IOException. When I went to "catch" the exception it said cannot find symbol IOException. This was fixed by import java.io.*;
I find that very weird conceptually. First System.in is wrapped by the System class. I have no need to import java.io.*; to use System so why would I need to import it in this case. Second, when I use Scanner to read in from System.in I do need to import java.io.*, yet I'm pretty sure it makes the same method calls to System.in I make, no?
//import java.io.*;
public class streams
     public static void main( String[] args )
          try {
               System.out.printf( "%c\n", System.in.read() );
          } catch (IOException e) {
               System.err.println( "IOException error" );
}

Answer 1

Importing does not make classes available. All it does is tell the compiler that when you say "IOException," it is actually shorthand for "java.io.IOException." The import applies only to the class in which it is declared, and only at compile time. It is gone once you compile your class. It does not show up in the .class file, and has no effect whatsoever at runtime.