Bug 73083 [Encoding] Need to verify encodings and indicate unavailable ones
When the encodings are set up we need to ensure that they are in the list of valid encodings available from the VM. Those that are not should be indicated as such and not be selectable in the UI.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/dialogs/AbstractEncodingFieldEditor.java
try {
			new String(new byte[0], enc);
			return true;
		} catch (UnsupportedEncodingException e) {
			return false;
		}
	}
	/**
	 * Return the default encoding.
	 * @return String
	 */
	protected String getDefaultEnc() {
		return defaultEnc;
	}
	/**
	 * Return whether or not the encoding setting changed.
	 * @param encodingSetting the setting from the page.
	 * @return boolean <code>true</code> if the resource encoding
	 * is the same as before.
	 */
	protected boolean hasSameEncoding(String encodingSetting) {
		String current = getStoredValue();
		if (encodingSetting == null) {
			
			return current == null || current.length() == 0;
		}
		return encodingSetting.equals(current);
	}
}