Bug 8476 JAR Packager: Make main class field editable
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarManifestWizardPage.java
}
		if (!fJarPackage.isMainClassValid(getContainer())) {
			setErrorMessage(JarPackagerMessages.getString("JarManifestWizardPage.error.invalidMainClass")); 
			return false;
		}
		if (incompleteButNotAnError) {
			setErrorMessage(null);
			return false;
		}
		
		setErrorMessage(null);
		return true;
	}
	/* 
	 * Implements method from IWizardPage.
	 */
	public void setPreviousPage(IWizardPage page) {
		super.setPreviousPage(page);
		if (getContainer() != null)
			updatePageCompletion();
	}
	/* 
	 * Implements method from IJarPackageWizardPage.
	 */
	public void finish() {
		saveWidgetValues();
	}
	
	/**
	 * Persists resource specification control setting that are to be restored