Add or substract hours to current time using Java Calendar

1. /*
2.   Add or substract hours to current time using Java Calendar
3.   This example shows how to add or substract hours in current time  
4.   using Java Calendar class.
5. */
6.  
7. import java.util.Calendar;
8.  
9. public class AddHoursToCurrentDate {
10.  
11.   public static void main(String[] args) {
12.    
13.     //create Calendar instance
14.     Calendar now = Calendar.getInstance();
15.  
16.     System.out.println("Current Date : " + (now.get(Calendar.MONTH) + 1)
17.                         + "-"
18.                         + now.get(Calendar.DATE)
19.                         + "-"
20.                         + now.get(Calendar.YEAR));
21.    
22.     System.out.println("Current time : " + now.get(Calendar.HOUR_OF_DAY)
23.                       + ":"
24.                       + now.get(Calendar.MINUTE)
25.                       + ":"
26.                       + now.get(Calendar.SECOND));
27.                      
28.     //add hours to current date using Calendar.add method
29.     now.add(Calendar.HOUR,10);
30.  
31.     System.out.println("New time after adding 10 hours : "
32.                       + now.get(Calendar.HOUR_OF_DAY)
33.                       + ":"
34.                       + now.get(Calendar.MINUTE)
35.                       + ":"
36.                       + now.get(Calendar.SECOND));
37.  
38.     /*
39.      * Java Calendar class automatically adjust the date accordingly if adding
40.      * hours to the current time causes current date to be changed.
41.      */
42.      
43.     System.out.println("New date after adding 10 hours : "
44.                         + (now.get(Calendar.MONTH) + 1)
45.                         + "-"
46.                         + now.get(Calendar.DATE)
47.                         + "-"
48.                         + now.get(Calendar.YEAR));
49.    
50.     //substract hours from current date using Calendar.add method
51.     now = Calendar.getInstance();
52.     now.add(Calendar.HOUR, -3);
53.  
54.     System.out.println("Time before 3 hours : " + now.get(Calendar.HOUR_OF_DAY)
55.                       + ":"
56.                       + now.get(Calendar.MINUTE)
57.                       + ":"
58.                       + now.get(Calendar.SECOND));
59.    
60.   }
61. }
62.  
63. /*
64. Typical output would be
65. Current Date : 12-25-2007
66. Current time : 18:31:42
67. New time after adding 10 hours : 4:31:42
68. New date after adding 10 hours : 12-26-2007
69. Time before 3 hours : 15:31:42
70. */