DrJava supports the use of different Java compilers, such as different versions of the "Javac" compiler supplied with the JDK. DrJava will attempt to locate the your Java compiler on startup by searching for standard installation directories, but sometimes it is unable to find a compiler. In this case, it will use the included Eclipse compiler instead. Note that the location of the compiler can be specified in the Preferences (see Configuring DrJava). If more than one compiler is specified, the active compiler can be selected from a menu on the Compiler Output tab itself.
DrJava will only display one compiler for each major version even though you have more than one update the JDK installed (Example: you have JDK 6 Updates 10 and 14 installed; DrJava will only display JDK 6 Update 14). If you want to display all compiler versions that were found, enable "Show all compiler versions" in the Preferences (see Configuring DrJava).
The preferred compiler can also be selected permanently by setting the Compiler Preference in the Compiler Options category of the Preferences. DrJava will then choose the selected compiler at startup.