1.使用stream求集合中对象的某2个属性的和
List<MacTicket> list = new ArrayList();
MacTicket ticket = new MacTicket();
ticket .setNum(1);
ticket.setAmount(2);
MacTicket ticket1 = new MacTicket();
ticket1.setNum(1);
ticket1.setAmount(2);
list.add(ticket);
list.add(ticket1);
int sum =list.stream().filter(tikcet->ticket.getNum()!=null&&ticket.getAmount()!=null).mapToInt(ticket->{return ticket.getNum()+ticket.getAmount();}).sum();
2.
https://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html