java-日期相減-計算秒數

Date dt1 = new Date("2009/6/2 18:00:04");
Date dt2 = new Date("2009/6/2 18:00:10");
Calendar calendar1 = new GregorianCalendar();
Calendar calendar2 = new GregorianCalendar();
calendar1.setTime(dt1);
calendar2.setTime(dt2);
System.out.println((calendar2.getTimeInMillis()-calendar1.getTimeInMillis())/1000);
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public static String datetime(String d1,String d2)
{
Date dt1 = new Date(d1);
Date dt2 = new Date(d2);
Calendar calendar1 = new GregorianCalendar();
Calendar calendar2 = new GregorianCalendar();
calendar1.setTime(dt1);
calendar2.setTime(dt2);
long l = (calendar2.getTimeInMillis()-calendar1.getTimeInMillis())/1000;
String s = String.valueOf(l);
return s;
}