Java日期计算、日期比较

获取当前时间

SimpleDateFormat df = new SimpleDateFormat(“yyyy-MM-dd HH:mm:ss”);//设置日期格式
String nowDate = df.format(new Date());// new Date()为获取当前系统时间

注:楼主一直以为date类型不如string类型随心所欲,所以下面的比较都是string类型的date进行比较。如果你真的真的就是那么倔强,ok,下面是date转string的方法:

SimpleDateFormat df = new SimpleDateFormat(“yyyy-MM-dd HH:mm:ss”);//设置日期格式
String date = df.format(Date类型的时间);

1.两个string类型的日期比较大小

public static int compare_date(String DATE1, String DATE2) {
DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
try {
Date dt1 = df.parse(DATE1);
Date dt2 = df.parse(DATE2);
if (dt1.getTime() > dt2.getTime()) {
System.out.println("dt1 在dt2前");
return 1;
} else if (dt1.getTime() < dt2.getTime()) {
System.out.println("dt1在dt2后");
return -1;
} else {
return 0;
}
} catch (Exception exception) {
exception.printStackTrace();
}
return 0;
}

2.返回两个string类型日期之间相差的天数

public static int daysBetween(String smdate,String bdate){
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
Calendar cal = Calendar.getInstance();
long time1 = 0;
long time2 = 0;

try{
cal.setTime(sdf.parse(smdate));
time1 = cal.getTimeInMillis();
cal.setTime(sdf.parse(bdate));
time2 = cal.getTimeInMillis();
}catch(Exception e){
e.printStackTrace();
}
long between_days=(time2-time1)/(1000*3600*24);

return Integer.parseInt(String.valueOf(between_days));
}

3.返回两个string类型日期相差的小时数

public static int daysBetween2(String startTime, String endTime) {
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH");
Calendar cal = Calendar.getInstance();
long time1 = 0;
long time2 = 0;

try{
cal.setTime(sdf.parse(startTime));
time1 = cal.getTimeInMillis();
cal.setTime(sdf.parse(endTime));
time2 = cal.getTimeInMillis();
}catch(Exception e){
e.printStackTrace();
}
long between_days=(time2-time1)/(1000*3600);

return Integer.parseInt(String.valueOf(between_days));
}

4.计算两段日期的重合日期

/**
* 计算两段日期的重合日期
* @param str1 开始日期1
* @param str2 结束日期1
* @param str3 开始日期2
* @param str4 结束日期2
* @return
* @throws Exception
*/
public static Map<String,Object> comparisonRQ(String str1, String str2, 
String str3,String str4) throws Exception {
String mesg = "";
DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
String startdate = "";
String enddate = "";
try {
Date dt1 = df.parse(str1);
Date dt2 = df.parse(str2);
Date dt3 = df.parse(str3);
Date dt4 = df.parse(str4);
if (dt1.getTime()<=dt3.getTime()&&dt3.getTime()<=dt2.getTime()&&
dt2.getTime()<=dt4.getTime()) {
mesg = "f";//重合
startdate = str3;
enddate = str2;
}
if (dt1.getTime()>=dt3.getTime()&&dt3.getTime()<=dt2.getTime()&&
dt2.getTime()<=dt4.getTime()) {
mesg = "f";//重合
startdate = str1;
enddate = str2;
}

if (dt3.getTime()<=dt1.getTime()&&dt1.getTime()<=dt4.getTime()&&
dt4.getTime()<=dt2.getTime()) {
mesg = "f";//重合
startdate = str1;
enddate = str4;
}
if (dt3.getTime()>=dt1.getTime()&&dt1.getTime()<=dt4.getTime()&&
dt4.getTime()<=dt2.getTime()) {
mesg = "f";//重合
startdate = str3;
enddate = str4;
}

System.out.println(startdate+"----"+enddate);

}catch (ParseException e) {
e.printStackTrace();
throw new ParseException(e.getMessage(), 0);
}catch(Exception e){
e.printStackTrace();
throw new Exception(e);
}
Map<String,Object> map = new HashMap<String,Object>();
map.put("startdate", startdate);
map.put("enddate", enddate);
return map;
}