Help: Issue on || and &&

Question

Hi
I wanted user to key in 'y', or 'Y' or 'N or 'n' ; so if it is not either one of this characters it will prompt a error message. However this statement I was using happen to satisfy the requirement.
if(choice.compareTo("y")!=0&&choice.compareTo("Y")!=0&&choice.compareTo("N")!=0&&choice.compareTo("n")!=0)
Why is this so? I thought the statement should be using ||,
if(choice.compareTo("y")!=0||choice.compareTo("Y")!=0||choice.compareTo("N")!=0||choice.compareTo("n")!=0)
Can anyone advise me on this?
import java.io.*;
class test1
public static void main(String args[])throws IOException
boolean flag=false;
BufferedReader in =new BufferedReader(new InputStreamReader(System.in));
while(!flag)
System.out.print("\nDo you wish to exit [Y/N]? ");
String choice = in.readLine();
if(choice.compareTo("y")!=0&&choice.compareTo("Y")!=0&&choice.compareTo("N")!=0&&choice.compareTo("n")!=0)
System.out.println("\n|| Please key in [Y/N] ||");
flag=false;
}else flag=true;
System.out.println("Out of Loop");
}

Answer 1

The latter two are also sometimes referred to as
"short-circuit" operators. See the
[url=http://java.sun.com/docs/books/jls/second_edition/
tml/expressions.doc.html#5228]Java Language
Specification for more detail.I had a lot of fun when first learning Perl trying to figure out other people's code:live ($free) || die[/code[