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
1 public static int compare_date(String DATE1, String DATE2) { 2 DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 3 try { 4 Date dt1 = df.parse(DATE1); 5 Date dt2 = df.parse(DATE2); 6 if (dt1.getTime() > dt2.getTime()) { 7 System.out.println("dt1 在dt2前"); 8 return 1; 9 } else if (dt1.getTime() < dt2.getTime()) {10 System.out.println("dt1在dt2后");11 return -1;12 } else {13 return 0;14 }15 } catch (Exception exception) {16 exception.printStackTrace();17 }18 return 0;19 }2.返回两个string类型日期之间相差的天数
1 public static int daysBetween(String smdate,String bdate){ 2 SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd"); 3 Calendar cal = Calendar.getInstance(); 4 long time1 = 0; 5 long time2 = 0; 6 7 try{ 8 cal.setTime(sdf.parse(smdate)); 9 time1 = cal.getTimeInMillis(); 10 cal.setTime(sdf.parse(bdate)); 11 time2 = cal.getTimeInMillis(); 12 }catch(Exception e){13 e.printStackTrace();14 }15 long between_days=(time2-time1)/(1000*3600*24); 16 17 return Integer.parseInt(String.valueOf(between_days)); 18 } 3.返回两个string类型日期相差的小时数
1 public static int daysBetween2(String startTime, String endTime) { 2 SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH"); 3 Calendar cal = Calendar.getInstance(); 4 long time1 = 0; 5 long time2 = 0; 6 7 try{ 8 cal.setTime(sdf.parse(startTime)); 9 time1 = cal.getTimeInMillis(); 10 cal.setTime(sdf.parse(endTime)); 11 time2 = cal.getTimeInMillis(); 12 }catch(Exception e){13 e.printStackTrace();14 }15 long between_days=(time2-time1)/(1000*3600); 16 17 return Integer.parseInt(String.valueOf(between_days)); 18 }4.计算两段日期的重合日期
1 /** 2 * 计算两段日期的重合日期 3 * @param str1 开始日期1 4 * @param str2 结束日期1 5 * @param str3 开始日期2 6 * @param str4 结束日期2 7 * @return 8 * @throws Exception 9 */10 public static Map<String,Object> comparisonRQ(String str1, String str2, String str3,11 String str4) throws Exception {12 String mesg = "";13 DateFormat df = new SimpleDateFormat("yyyy-MM-dd");14 String startdate = "";15 String enddate = "";16 try {17 Date dt1 = df.parse(str1);18 Date dt2 = df.parse(str2);19 Date dt3 = df.parse(str3);20 Date dt4 = df.parse(str4);21 if (dt1.getTime()<=dt3.getTime()&&dt3.getTime()<=dt2.getTime()&&dt2.getTime()<=dt4.getTime()) {22 mesg = "f";//重合23 startdate = str3;24 enddate = str2;25 }26 if (dt1.getTime()>=dt3.getTime()&&dt3.getTime()<=dt2.getTime()&&dt2.getTime()<=dt4.getTime()) {27 mesg = "f";//重合28 startdate = str1;29 enddate = str2;30 }31 32 if (dt3.getTime()<=dt1.getTime()&&dt1.getTime()<=dt4.getTime()&&dt4.getTime()<=dt2.getTime()) {33 mesg = "f";//重合34 startdate = str1;35 enddate = str4;36 }37 if (dt3.getTime()>=dt1.getTime()&&dt1.getTime()<=dt4.getTime()&&dt4.getTime()<=dt2.getTime()) {38 mesg = "f";//重合39 startdate = str3;40 enddate = str4;41 }42 43 System.out.println(startdate+"----"+enddate);44 45 46 }catch (ParseException e) {47 e.printStackTrace();48 throw new ParseException(e.getMessage(), 0);49 }catch(Exception e){50 e.printStackTrace();51 throw new Exception(e);52 }53 Map<String,Object> map = new HashMap<String,Object>();54 map.put("startdate", startdate);55 map.put("enddate", enddate);56 return map;57 }
原标题：java日期比较，日期计算
关键词：JAVA
我知道了 