checking source and giving permission

is it possible to do this?

if("linkingfrom".equals(www.google.com)){
output+= "alert('Granted Access');"; }
else{
output+= "alert('You do not have permission to enter this page.');
}

what do i put in for linking from??

Thanks Tony

if(/www.google.com/.test(document.referrer))...

i'm using the code:

if(/www.google.com/.test(document.referrer)){
output+= "alert('Granted Access');"; }
else{
output+= "alert('You do not have permission to enter this page.');";
}

and getting these errors...
>javac aiaccess_dev.java
aiaccess_dev.java:1065: illegal start of expression
if(/www.google.com/.test(document.referrer)){
^
aiaccess_dev.java:1072: ')' expected
String folder_code = null;
^
2 errors
what to do ??

Sorry- I forgot to escape the periods
if(/www\.google\.com/.test(document.referrer))

But you don't get an error with either expression in javascript-
If you are doing this in java you are posting in the wrong forum...
javascript really isn't java...