Bug 13269 Incorrect operation order in jarpackager
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarFileExportOperation.java
IFile[] classFiles= fJarPackage.findClassfilesFor(file);
		if (classFiles != null)
			return Arrays.asList(classFiles).iterator();
		if (!isJavaFile(file))
			return Collections.EMPTY_LIST.iterator();
		
		IPath outputPath= javaProject.getOutputLocation();
		IContainer outputContainer;		
		if (javaProject.getProject().getFullPath().equals(outputPath))
			outputContainer= javaProject.getProject();
		else {
			outputContainer= createFolderHandle(outputPath);
			if (outputContainer == null || !outputContainer.isAccessible()) {
				String msg= JarPackagerMessages.getString("JarFileExportOperation.outputContainerNotAccessible"); 
				throw new CoreException(new Status(IStatus.ERROR, JavaPlugin.getPluginId(), JavaStatusConstants.INTERNAL_ERROR, msg, null));
			}
		}
		
		boolean hasErrors= hasCompileErrors(file);
		boolean hasWarnings= hasCompileWarnings(file);
		boolean canBeExported= canBeExported(hasErrors, hasWarnings);
		if (!canBeExported)
			return Collections.EMPTY_LIST.iterator();
		reportPossibleCompileProblems(file, hasErrors, hasWarnings, canBeExported);
		IContainer classContainer= outputContainer;
		if (pathInJar.segmentCount() > 1)
			classContainer= outputContainer.getFolder(pathInJar.removeLastSegments(1));
			
		if (fExportedClassContainers.contains(classContainer))