java Date操作

//获得本年第一天的日期 
public Date getCurrentYearFirst(){
int yearPlus = getYearPlus();
GregorianCalendar currentDate = new GregorianCalendar();
currentDate.add(GregorianCalendar.DATE,yearPlus);
Date yearDay = currentDate.getTime();
Calendar calendar =  Calendar.getInstance();
calendar.setTime(yearDay);  
calendar.set(Calendar.HOUR, 0);     //0时
calendar.set(Calendar.MINUTE, 0);     //0分
calendar.set(Calendar.SECOND, 0);     //0秒
yearDay = calendar.getTime();
return yearDay;
}
//获得今年的年份
private int getYearPlus(){
Calendar cd = Calendar.getInstance();
int yearOfNumber = cd.get(Calendar.DAY_OF_YEAR);//获得当天是一年中的第几天
cd.set(Calendar.DAY_OF_YEAR,1);//把日期设为当年第一天
cd.roll(Calendar.DAY_OF_YEAR,-1);//把日期回滚一天。
int MaxYear = cd.get(Calendar.DAY_OF_YEAR);
if(yearOfNumber == 1){
return -MaxYear;
}else{
return 1-yearOfNumber;
}
}
//判断beginDate 至 endDate 是否包含 betweentDate
private boolean betweentTowDate(Date beginDate,Date betweentDate,Date endDate){
if(null==beginDate||null==endDate||null==betweentDate){
return false;
}
if(beginDate.getTime()<betweentDate.getTime()&&endDate.getTime()>betweentDate.getTime()){
return true;
}else{
return false;
}
}
//判断beginDate1至endDate1时间段是否与beginDate2至endDate2时间段有交集
private boolean intersectTime(Date beginDate1,Date endDate1,Date beginDate2,Date endDate2){
if(null==beginDate1||null==endDate1||null==beginDate2||null==endDate2){
return false;
}
long a1 = beginDate1.getTime();
long a2 = endDate1.getTime();
long b1 = beginDate2.getTime();
long b2 = endDate2.getTime();
if((a2<=b2 && a2>=b1) || (a1<=b2 && a1>=b1)  || (b1<a1 && b2>a2)){
return true;
}else{
return false;
}
}