public static ZHConverter getInstance(int converterType) {

		if (converterType >= 0 && converterType < NUM_OF_CONVERTERS) {

			if (converters[converterType] == null) {
				synchronized (ZHConverter.class) {
					if (converters[converterType] == null) {
						converters[converterType] = new ZHConverter(
								propertyFiles[converterType]);
					}
				}
			}
			return converters[converterType];

		} else {
			return null;
		}
	}