db is an instance of org.mozilla.javascript.tools.debugger.Main, which inherits ContextListener.
org.mozilla.javascript.tools.debugger.Main inherits JFrame, and implements ContextListener (not inherits), and Debugger
setOptimizationLevel() is defined within org.mozilla.javascript.Context.
ContextListener doesn't inherit Context, which is the file that is imported in JavaScriptInterpreter.java.
I recommend either changing
import org.mozilla.javascript.Context => import org.mozilla.javascript.ContextListener
Or the safer bet would be to just add another import statement for ContextListener.
I believe this solution will fix both files (JavaScriptInterpreter.java, and FOM_JavaScriptInterpreter.java)
Well my belief was way off.
setOptimizationLevel is public, but I fail to see where db, an instance of org.mozilla.javascript.tools.debugger.Main, is inheriting the method.
M. J. Stahl
"I must create a system, or be enslaved by another man's."
-- William Blake