常用的java日期比较和日期计算方法小结

本文为大家分享的都是常用的日期之间的比较方法，供以后参考。 

热身：获取当前时间 

simpledateformat df = new simpledateformat("yyyy-mm-dd hh:mm:ss");//设置日期格式
string nowdate = df.format(new date());// new date()为获取当前系统时间 

注：楼主一直以为date类型不如string类型随心所欲，所以下面的比较都是string类型的date进行比较。如果你真的真的就是那么倔强，ok，下面是date转string的方法： 

simpledateformat df = new simpledateformat("yyyy-mm-dd hh:mm:ss");//设置日期格式
string date = df.format(date类型的时间); 

1.两个string类型的日期比较大小 

public static int compare_date(string date1, string date2) {
     dateformat df = new simpledateformat("yyyy-mm-dd hh:mm:ss");
     try {
       date dt1 = df.parse(date1);
       date dt2 = df.parse(date2);
       if (dt1.gettime() > dt2.gettime()) {
         system.out.println("dt1 在dt2前");
         return 1;
       } else if (dt1.gettime() < dt2.gettime()) {
         system.out.println("dt1在dt2后");
         return -1;
       } else {
         return 0;
       }
     } catch (exception exception) {
       exception.printstacktrace();
     }
     return 0;
   }

2.返回两个string类型日期之间相差的天数 

public static int daysbetween(string smdate,string bdate){ 
     simpledateformat sdf=new simpledateformat("yyyy-mm-dd"); 
     calendar cal = calendar.getinstance();  
     long time1 = 0;
     long time2 = 0;
     
     try{
       cal.settime(sdf.parse(smdate));  
       time1 = cal.gettimeinmillis();  
       cal.settime(sdf.parse(bdate)); 
       time2 = cal.gettimeinmillis(); 
     }catch(exception e){
       e.printstacktrace();
     }
     long between_days=(time2-time1)/(1000*3600*24); 
       
    return integer.parseint(string.valueof(between_days));   
   }

3.返回两个string类型日期相差的小时数 

public static int daysbetween2(string starttime, string endtime) {
     simpledateformat sdf=new simpledateformat("yyyy-mm-dd hh"); 
     calendar cal = calendar.getinstance();  
     long time1 = 0;
     long time2 = 0;
     
     try{
        cal.settime(sdf.parse(starttime));  
        time1 = cal.gettimeinmillis();  
        cal.settime(sdf.parse(endtime)); 
        time2 = cal.gettimeinmillis(); 
     }catch(exception e){
       e.printstacktrace();
     }
     long between_days=(time2-time1)/(1000*3600); 
       
     return integer.parseint(string.valueof(between_days));   
   }

4.计算两段日期的重合日期 

/**
   * 计算两段日期的重合日期
   * @param str1 开始日期1
   * @param str2 结束日期1
   * @param str3 开始日期2
   * @param str4 结束日期2
   * @return
   * @throws exception
   */
  public static map<string,object> comparisonrq(string str1, string str2, string str3,
      string str4) throws exception {
    string mesg = "";
    dateformat df = new simpledateformat("yyyy-mm-dd");
    string startdate = "";
    string enddate = "";
    try {
      date dt1 = df.parse(str1);
      date dt2 = df.parse(str2);
      date dt3 = df.parse(str3);
      date dt4 = df.parse(str4);
      if (dt1.gettime()<=dt3.gettime()&&dt3.gettime()<=dt2.gettime()&&dt2.gettime()<=dt4.gettime()) {
        mesg = "f";//重合
        startdate = str3;
        enddate = str2;
      }
      if (dt1.gettime()>=dt3.gettime()&&dt3.gettime()<=dt2.gettime()&&dt2.gettime()<=dt4.gettime()) {
        mesg = "f";//重合
        startdate = str1;
        enddate = str2;
      }
      
      if (dt3.gettime()<=dt1.gettime()&&dt1.gettime()<=dt4.gettime()&&dt4.gettime()<=dt2.gettime()) {
        mesg = "f";//重合
        startdate = str1;
        enddate = str4;
      }
      if (dt3.gettime()>=dt1.gettime()&&dt1.gettime()<=dt4.gettime()&&dt4.gettime()<=dt2.gettime()) {
        mesg = "f";//重合
        startdate = str3;
        enddate = str4;
      }
      
      system.out.println(startdate+"----"+enddate);
      
      
    }catch (parseexception e) {
      e.printstacktrace();
      throw new parseexception(e.getmessage(), 0);
    }catch(exception e){
      e.printstacktrace();
      throw new exception(e);
    }
    map<string,object> map = new hashmap<string,object>();
    map.put("startdate", startdate);
    map.put("enddate", enddate);
    return map;
  }

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。