java-一個月的第一天和最後一天

/**
	 * 
	 * @param year
	 *            int 年份
	 * @param month
	 *            int 月份
	 * 
	 * @return int 某年某月的最後一天
	 */
	private int getLastDayOfMonth(int year, int month) {
		Calendar cal = Calendar.getInstance();
		cal.set(Calendar.YEAR, year);
		cal.set(Calendar.MONTH, month);
		// 某年某月的最後一天
		return cal.getActualMaximum(Calendar.DATE);
	}

需要注意的是：月份是從0開始的，比如說如果輸入5的話，實際上顯示的是4月份的最後一天，千萬不要搞錯了哦

Calendar calendar = Calendar.getInstance(); //得到月初 calendar.set(Calendar.DAY_OF_MONTH,calendar.getActualMinimum(Calendar.DAY_OF_MONTH)); Date strDateFrom = calendar.getTime(); //得到月末 calendar.set(Calendar.DAY_OF_MONTH,calendar.getActualMaximum(Calendar.DAY_OF_MONTH)); Date strDateTo = calendar.getTime();

/**  
 * 得到本月的第一天  
 * @return  
 */  
public static String getMonthFirstDay() {   
    Calendar calendar = Calendar.getInstance();   
    calendar.set(Calendar.DAY_OF_MONTH, calendar   
            .getActualMinimum(Calendar.DAY_OF_MONTH));   
  
    return dateFormat("yyyy-MM-dd", calendar.getTime());   
}   
  
/**  
 * 得到本月的最後一天  
 *   
 * @return  
 */  
public static String getMonthLastDay() {   
    Calendar calendar = Calendar.getInstance();   
    calendar.set(Calendar.DAY_OF_MONTH, calendar   
            .getActualMaximum(Calendar.DAY_OF_MONTH));   
    return dateFormat("yyyy-MM-dd", calendar.getTime());   
}