Java单例模式实现自动编号，防重复生成

package com.mars.web.paymentWeb;


import com.mars.core.base.BaseController;
import com.mars.service.paymentWeb.WebContractService;
import freemarker.template.utility.StringUtil;
import org.springframework.beans.factory.annotation.Autowired;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.HashMap;
import java.util.Map;

/**
 * 自动生成合同编号
 * Created by zhaoxj on 2017/6/22.
 */
public class HtCodeFactory{
    private static Map<String,String> mapOrder = new HashMap<String,String>();
    public synchronized static String getResNumber(String htbh){
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy");
        String code=mapOrder.get("curCode");
        Calendar c=Calendar.getInstance();

        if(code==null){
            int year=c.get(Calendar.YEAR);
           // WebCoalService  coalservice=(WebCoalService)SpringWebApplicationContextUtil.context.getBean("CoalService");
           // String dbcode="";//coalservice.getFspcodeByDate(day);
            if(null==htbh || "".equals(htbh)){