计算时间差

SimpleDateFormat来实现，比较简单，直接拿来用。

首先我们先初始化我们的SimpleDateFormat

SimpleDateFormat simpleFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm");//如2016-08-10 20:40

1.计算天数差。

String fromDate = simpleFormat.format("2016-05-01 12:00");
String toDate = simpleFormat.format("2016-06-01 12:00");
long from = simpleFormat.parse(fromDate).getTime();
long to = simpleFormat.parse(toDate).getTime();
int days = (int) ((to - from)/(1000 * 60 * 60 * 24));

2.计算小时差

String fromDate = simpleFormat.format("2016-05-01 12:00");
String toDate = simpleFormat.format("2016-05-01 14:00");
long from = simpleFormat.parse(fromDate).getTime();
long to = simpleFormat.parse(toDate).getTime();
int hours = (int) ((to - from)/(1000 * 60 * 60));

3.计算分钟差：

String fromDate = simpleFormat.format("2016-05-01 12:00");
String toDate = simpleFormat.format("2016-05-01 12:50");
long from = simpleFormat.parse(fromDate).getTime();
long to = simpleFormat.parse(toDate).getTime();
int minutes = (int) ((to - from)/(1000 * 60));