1. A Java Collection interface that simply tracks whether elements are in a Collection or not, but nothing else. The most common implemetation is HashSet.
2. The SET environment is a also feature of DOS and W95/W98/Me/NT/W2K/XP/W2K3/Vista to pass large numbers of parameters to programs. It is not directly suppored by Java since there is no equivalent in other operating systems. You can use JNI to get at it, or exec, or you can snaffle set parms and pass them in the java.exe command line with the -D option. Java Properties take the place of Windows SET environment and INI files. You could also read them capturing output of an exec 'ed SET . To set them would require some JNI. In NT/W2K/XP/W2K3 they are stored in the registry. Set variables are supposed to be case insensitive, but they are not quite. Traditionally they are written all upper case. Don’t put quotes around the SET value, even when it contains spaces, but put them around the set variable and comparing value in an IF statement: e.g.

   SET CUSTOMER=Roedy Green
   IF "%CUSTOMER%" == "Roedy Green" Echo That's me

   You might try to set an environment variable by execing a SET command. This won’t work, since the set environment is restored as soon as exec terminates. The SETs you do in a bat file are only good inside that bat file for the time the bat file in running.
3. Mastercard and Visa’s under-development protocol for sending encrypted credit card numbers over the net. What makes it interesting in that the merchant never gets to know your credit card number — only the bank does. This will cut out most credit card fraud.

Learning More