public double avgCourse(String course, List<Student> ls) {
double sum = 0;
int size = 0;
for (Iterator<Student> it = ls.iterator(); it.hasNext();) {//hasNext返回一个布尔值
Student s = it.next();
if (s.getCourse() == course) {
sum += s.getScore();
size++;
}
}
return sum / size;
}
这程序中Iterator<Student> it = ls.iterator(); it.hasNext();是什么意思 Student s = it.next();什么意思,不懂哪些函数是java自带的 哪些是自己写的