java日期操作

   import java.text.SimpleDateFormat;
   import java.util.Calendar;
   import java.util.Date;
   import java.util.GregorianCalendar;
  5
  6/** *//**
  7 *
  8 * @author zzk
  9 *
10 */
11public class DateUtil {
12
13    /** *//**
14     * 取得某天相加(减)後的那一天
15     *
16     * @param date
17     * @param num(可正可负)
18     * @return
19     */
20    public static Date getAnotherDate(Date date, int num) {
21        Calendar c = Calendar.getInstance();
22        c.setTime(date);
23        c.add(Calendar.DAY_OF_YEAR, num);
24        return c.getTime();
25    }
26
27    /** *//**
28     * 取得某月的的最后一天
29     *
30     * @param year
31     * @param month
32     * @return
33     */
34    public static Date getLastDayOfMonth(int year, int month) {
35        Calendar cal = Calendar.getInstance();
36        cal.set(Calendar.YEAR, year);// 年
37        cal.set(Calendar.MONTH, month - 1);// 月，因为Calendar里的月是从0开始，所以要减1
38        cal.set(Calendar.DATE, 1);// 日，设为一号
39        cal.add(Calendar.MONTH, 1);// 月份加一，得到下个月的一号
40        cal.add(Calendar.DATE, -1);// 下一个月减一为本月最后一天
41        return cal.getTime();// 获得月末是几号
42    }
43
44    /** *//**
45     * 取得某天是一年中的多少周
46     *
47     * @param date
48     * @return
49     */
50    public static int getWeekOfYear(Date date) {
51        Calendar c = new GregorianCalendar();
52        c.setFirstDayOfWeek(Calendar.MONDAY);
53        c.setMinimalDaysInFirstWeek(7);
54        c.setTime(date);
55        return c.get(Calendar.WEEK_OF_YEAR);
56    }
57
58    /** *//**
59     * 取得某天所在周的第一天
60     *
61     * @param date
62     * @return
63     */
64    public static Date getFirstDayOfWeek(Date date) {
65        Calendar c = new GregorianCalendar();
66        c.setFirstDayOfWeek(Calendar.MONDAY);
67        c.setTime(date);
68        c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek());
69        return c.getTime();
70    }
71
72    /** *//**
73     * 取得某天所在周的最后一天
74     *
75     * @param date
76     * @return
77     */
78    public static Date getLastDayOfWeek(Date date) {
79        Calendar c = new GregorianCalendar();
80        c.setFirstDayOfWeek(Calendar.MONDAY);
81        c.setTime(date);
82        c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek() + 6);
83        return c.getTime();
84    }
85
86    /** *//**
87     * 取得某一年共有多少周
88     *
89     * @param year
90     * @return
91     */
92    public static int getMaxWeekNumOfYear(int year) {
93        Calendar c = new GregorianCalendar();
94        c.set(year, Calendar.DECEMBER, 31, 23, 59, 59);
95        return getWeekOfYear(c.getTime());
96    }
97   
98    /** *//**
99     * 取得某年某周的第一天
100     * 对于交叉:2008-12-29到2009-01-04属于2008年的最后一周,2009-01-05为2009年第一周的第一天
101     * @param year
102     * @param week
103     * @return
104     */
105    public static Date getFirstDayOfWeek(int year, int week) {
106        Calendar calFirst = Calendar.getInstance();
107        calFirst.set(year, 0, 7);
108        Date firstDate = getFirstDayOfWeek(calFirst.getTime());
109
110        Calendar firstDateCal = Calendar.getInstance();
111        firstDateCal.setTime(firstDate);
112
113        Calendar c = new GregorianCalendar();
114        c.set(Calendar.YEAR, year);
115        c.set(Calendar.MONTH, Calendar.JANUARY);
116        c.set(Calendar.DATE, firstDateCal.get(Calendar.DATE));
117
118        Calendar cal = (GregorianCalendar) c.clone();
119        cal.add(Calendar.DATE, (week - 1) * 7);
120        firstDate = getFirstDayOfWeek(cal.getTime());
121
122        return firstDate;
123    }
124
125    /** *//**
126     * 取得某年某周的最后一天
127     * 对于交叉:2008-12-29到2009-01-04属于2008年的最后一周,
         2009-01-04为 2008年最后一周的最后一天
128     * @param year
129     * @param week
130     * @return
131     */
132    public static Date getLastDayOfWeek(int year, int week) {
133        Calendar calLast = Calendar.getInstance();
134        calLast.set(year, 0, 7);
135        Date firstDate = getLastDayOfWeek(calLast.getTime());
136
137        Calendar firstDateCal = Calendar.getInstance();
138        firstDateCal.setTime(firstDate);
139
140        Calendar c = new GregorianCalendar();
141        c.set(Calendar.YEAR, year);
142        c.set(Calendar.MONTH, Calendar.JANUARY);
143        c.set(Calendar.DATE, firstDateCal.get(Calendar.DATE));
144
145        Calendar cal = (GregorianCalendar) c.clone();
146        cal.add(Calendar.DATE, (week - 1) * 7);
147        Date lastDate = getLastDayOfWeek(cal.getTime());
148       
149        return lastDate;
150    }
151}
152    /**
         *获取当前日期的年、月、日
           */
        public void  display(){
Calendar cal = Calendar.getInstance();
//年
int year=cal.get(cal.YEAR);
//月
int  month=cal.get(cal.MONTH)+1;
//日
int date=cal.get(cal.DATE);
                  //星期
                     int today=cal.get(cal.DAY_OF_WEEK)-1;
}