DrJava supports the use of different Java compilers, such as the traditional "Javac" compiler supplied with the JDK or Sun's JSR-14 experimental compiler (which supports generic types when only running under the 1.4 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 prompt you to specify the location of a compiler, or allow you to continue using DrJava without any compiler. 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. You may notice that the same compiler may appear multiple times in the menu. This happens because DrJava looks for compilers in three different places: on the user classpath, the user specified location in Preferences, and in the usual locations that the compiler can be found (the default installation directory, where java is located, etc.).