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都是常用的日期之間的比較方法，供以後參考。
熱身：擷取目前時間
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//設定日期格式
String nowDate = df.format(new Date());// new Date()為擷取目前系統時間
注：樓主一直以為date類型不如string類型随心所欲，是以下面的比較都是string類型的date進行比較。如果你真的真的就是那麼倔強，ok，下面是date轉string的方法：
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//設定日期格式
String date = df.format(Date類型的時間);
1.兩個string類型的日期比較大小
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後");
11 return -1;
12 } else {
13 return 0;
14 }
15 } catch (Exception exception) {
16 exception.printStackTrace();
17 }
18 return 0;
19 } 2.傳回兩個string類型日期之間相差的天數
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.傳回兩個string類型日期相差的小時數
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.計算兩段日期的重合日期
1 /**
2 * 計算兩段日期的重合日期
3 * @param str1 開始日期1
4 * @param str2 結束日期1
5 * @param str3 開始日期2
6 * @param str4 結束日期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 }