SET : Java Glossary

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 files to set the value of a script variable. The SET environment is a feature of DOS and W95/W98/Me/NT/W2K/XP/W2K3/Vista/W7 to pass large numbers of parameters to programs. It is only half-heartedly suppored by Java with System.getEnv. There is 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.

Tips

• Set variables are supposed to be case insensitive, but they are not quite. Traditionally they are written all upper case. To make them more portable, you are best to think of them as case-sensitive.
• 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

Gotchas

• In the DOS days you could optionally put spaces around the equal sign in a SET command. Now, at least in TakeCommand, you cannot. You must leave them out. If you put them in, you create variable names with trailing spaces, or values with lead spaces.
• 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.
• Restart any command prompt boxes after making changes to the environment. Reboot if your changes would affect any programs started with the task manager.

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