java日期比較，日期計算，java日期比較計算

java日期比較，日期計算，java日期比較計算

都是常用的日期之間的比較方法，供以後參考。

熱身：獲取當前時間

SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//設置日期格式
String nowDate = df.format(new Date());// new Date()為獲取當前系統時間

注：樓主一直以為date類型不如string類型隨心所欲，所以下面的比較都是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");//設置日期格式
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.返回兩個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.返回兩個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     }