Why does Java use -D to indicate system properties?

Why is th开发者_Python百科e flag that indicates a System property in Java -D? Surely there is some semantics to this letter choice, but I can't guess what it is.

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It is short for setting a system define.

"define" debug to yes

-Ddebug=yes

There is some historical context, as other compilers use similar flags. For example, gcc uses -D to set a preprocessor define.

gcc -D debug=yes test.c

will compile test.c with a preprocessing environment where the preprocessor variable debug is set to yes.

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"defines" properties. Properties aren't arguments, so you'd need a special identifier anyway.