单例模式(singleton)的一种写法

public class ModbusDetailsRequest {
    private final ReadInputRegistersRequest request;

    private static class ModbusDetailsRequestLoader {
        private static final ModbusDetailsRequest INSTANCE = new ModbusDetailsRequest();

        private ModbusDetailsRequestLoader() {
        }
    }

    private ModbusDetailsRequest() {
        this.request = new ReadInputRegistersRequest();
    }

    public static ModbusDetailsRequest getInstance() {
        return ModbusDetailsRequestLoader.INSTANCE;
    }

   
    public ModbusRequest getRequest(final DeviceRequestConfig config) {
        request.setReference(config.getRef());
        request.setWordCount(config.getCount());
        request.setUnitID(config.getUnitId());
        return request;
    }

}