Bug 94367 cannot clear compiler compliance setting at the project level
i200505092010 Cannot disable the Java compiler project-specific preferences for some projects. Steps to reproduce: 1 - check out from CVS a Java project that has project-specific Java compiler settings enabled (example: org.eclipse.core.runtime). 2 - open the properties dialog for the project, select the Java compiler node, disable project-specific Java compiler preferences. 3 - Commit the changes by pressing "Ok" and reopen the properties dialog. It looks like the settings were not saved (project-specific settings are still enabled).
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/OptionsConfigurationBlock.java
if (doBuild) { 
				container.registerUpdateJob(CoreUtility.getBuildJob(fProject));
			}
		} else {
			
			try {
				fManager.applyChanges();
			} catch (BackingStoreException e) {
				JavaPlugin.log(e);
				return false;
			}
			if (doBuild) {
				CoreUtility.getBuildJob(fProject).schedule();
			}
			
		}
		return true;
	}
	
	protected abstract String[] getFullBuildDialogStrings(boolean workspaceSettings);
			
	
	public void performDefaults() {
		DefaultScope defaultScope= new DefaultScope();
		for (int i= 0; i < fAllKeys.length; i++) {
			Key curr= fAllKeys[i];
			String defValue= curr.getStoredValue(defaultScope, null);
			curr.setStoredValue(fLookupOrder[0], defValue, fManager);
		}