Unable to locate the Javac Compiler in: C:\Program Files\Java\jre6\..\lib\tools.jar Please ensure you are using JDK 1.4 or above and not a JRE (the com.sun.tools.javac.Main class is required). In most cases you can change the location of your Java installation by setting the JAVA_HOME environment variable.
The solution that worked for me (tested on both 32- and 64-bit Eclipse/Java) was not to change the
eclipse.ini, but to instead set the Runtime JRE on the JRE tab of the Run/Debug Configuration dialog to use the appropriate JDK, either as the “Workspace default JRE” or the “Alternate JRE”
Does that work for anybody else?