hi sathi
Also, when i read an example, this features let us know things like "file.separator","java.class.path","java.class.version","os.name"...etc. why do we need to know these at run time? we need to have them at run time in case we want to migrate code across various platforms.
for e.g. if we code using file separator as "/" which is for Unix based systems then we have to change it when we give our program to a friend running windows as the file separator is "\" on windows.
well, u might think this is just a little change but its better to avoid that as well in cases when v r going to provide the compiled classes ONLY to the others for running them and we don't know which system they have...
to give u an example of the use of "runtime" properties,
there r some java properties which certain APIs uses and we can specify their values using switches like "-D" at runtime. u can go to,
RMI tutorial page which one of the many examples how ppl use "-D" switch and specify property values at run time for,
java.rmi.server.codebase etc...
u can use those properties with System.getProperty("java.rmi.server.codebase") as well...u know..
hope u c some direction here
regards
maulin