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Just curious as to when System.getProperty("java.io.tmpdir") returns "c:\temp" . According to the java.io.File Java Docs -

The default temporary-file directory is specified by the system property java.io.tmpdir. On UNIX systems the default value of this property is typically "/tmp" or "/var/tmp"; on Microsoft Windows systems it is typically "c:\temp". A different value may be given to this system property when the Java virtual machine is invoked, but programmatic changes to this property are not guaranteed to have any effect upon the the temporary directory used by this method.

But in my case-

System.out.println(System.getProperty("java.io.tmpdir"));
Always returns-
C:\Users\admin\AppData\Local\Temp\ i.e. %TEMP%
In what conditions will it return "c:\temp"? 
EDITED: If I change %TEMP% to C:\Temp then I will get C:\Temp, right? But the documentation shows c:\Temp instead of C:\Temp. 
                en.wikipedia.org/wiki/Temporary_folder Looking at the wiki, I'd say you can make it C:\Temp by changing %TEMP%, installing Windows 98 or passing it to java -Djava.io.tmpdir=C:\Temp. Also check out this: stackoverflow.com/questions/3437095/…
– bezmax
                May 3, 2013 at 5:43
                @Max Thanks MAX. If I change %TEMP% to C:\Temp then I will get C:\Temp. Right? but doc show c:\Temp instead of C:\Temp. :)
– Ashish Pancholi
                May 3, 2013 at 5:50
                The 1.4.2 Javadoc you are linking to is outdated. The current 7 Javadoc mentions a "typical" directory of "C:\\WINNT\\TEMP".
– Abdull
                Aug 5, 2013 at 14:22
In MS Windows  the temporary directory is set by the environment variable TEMP. In XP, the temporary directory was set per-user as Local Settings\Temp.
If you change your TEMP environment variable to C:\temp, then you get the same when you run :
System.out.println(System.getProperty("java.io.tmpdir"));
                On Windows there is a second environment variable called %TMP% and it is this which is sometimes used, not %TEMP%, for example the GWT plugin for Eclipse uses the %TMP% variable.
– Wee Shetland
                Oct 10, 2013 at 12:15
                @Joshi : Your answer is quite accurate. However, I disagree with the example you gave : If the user set the TMP env var, then the TEMP will be ignored. Please, refer to my answer and let me know if you didn't understood what I mean.
– Zakaria
                Apr 18, 2015 at 11:43
On the one hand, when you call System.getProperty("java.io.tmpdir") instruction, Java calls the Win32 API's function GetTempPath.
According to the MSDN :
  
The GetTempPath function checks for the existence of environment
  variables in the following order and uses the first path found:
  
The path specified by the TMP environment variable.
  
The path specified by the TEMP environment variable.
  
The path specified by the USERPROFILE environment variable.
  
The Windows directory.
On the other hand, please check the historical reasons on why TMP and TEMP coexist. It's really worth reading.
Value of %TEMP% environment variable is often user-specific and Windows sets it up with regard to currently logged in user account. Some user accounts may have no user profile, for example when your process runs as a service on SYSTEM, LOCALSYSTEM or other built-in account, or is invoked by IIS application with AppPool identity with Create user profile option disabled. So even when you do not overwrite %TEMP% variable explicitly, Windows may use c:\temp or even c:\windows\temp folders for, lets say, non-usual user accounts. And what's more important, process might have no access rights to this directory!
        
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