Java 1.5 Tiger A Developers Notebook [Electronic resources] نسخه متنی

8.5 Shadowing Static Imports

As a final act of complete

confusion in your code, you're welcome to
shadow your imports, static or otherwise. Shadowing is the process of
having a member variable (or field, or method) effectively hide something
that is already in the Java namespace through an import.

8.5.1 How do I do that?

Simply declare a member variable named the same as what is imported,
and that you want to shadow. Example 8-4 is an example of just that
process in action.

Example 8-4. Shadowing an import

package com.oreilly.tiger.ch08;
import static java.lang.System.err;
import static java.lang.System.out;
import java.io.IOException;
import java.io.PrintStream;
public class StaticImporter {
public static void writeError(PrintStream err, String msg)
throws IOException {
// Note that err in the parameter list overshadows the imported err
err.println(msg);
}
public static void main(String[] args) {
if (args.length < 2) {
err.println(
"Incorrect usage: java com.oreilly.tiger.ch08 [arg1] [arg2]");
return;
}
out.println("Good morning, " + args[0]);
out.println("Have a " + args[1] + " day!");
try {
writeError(System.out, "Error occurred.");
} catch (IOException e) {
e.printStackTrace( );
}
}
}

NOTE

Example 8-4 is an
updated version
of Example 8-1.

Note that a variable named err is defined, local to the writeError( )
method. That variable, in that method, will shadow the err variable
imported from java.lang.System. Keep in mind, though, that this adds
yet another layer of obfuscation to your code. It's almost always easier to
just rename your variable to avoid this type of confusion, and save everyone
some headaches:

     public static void writeError(PrintStream errorStream, String msg)
throws IOException {
errorStream.println(msg);
}