SET : Java Glossary


Set
Set has at least three meanings:
  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. Most of the operations you do on your Sets will be methods of Collection.
  2. 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.
  3. A command in Windows BAT (Batch) files to set the value of a script variable. The SET environment is a feature of DOS (Disk Operating System) and W95/W98/Me/NT/W2K/XP/W2003/Vista/W2008/W7-32/W7-64/W8-32/W8-64 to pass large numbers of parameters to programs. It is only half-heartedly suppored by Java with System.getEnv. There is no equivalent in other operating systems. It is getenv not getEnv. You can use JNI (Java Native Interface) 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.

Tips

Gotchas

Learning More

Oracle’s Javadoc on Set class : available:
Oracle’s Javadoc on Collections.unmodifiableSet : available:
Oracle’s Javadoc on Collections.emptySet : available:

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