After so many years of study, I found a problem, as if teachers are very fond of roll call, even the roll call has become some of the teacher's hobby, a day does not call, on the food does not smell, sleep is not good, I feel very strange, your class if you speak well, how can students do not come to the lectures, but: "Fraught, is a crime!" "Ah.
Okay, so let's see the teacher now. How does this roll-call process come true:
1, the old rules, we first define the teacher (Teacher) interface class:
Copy Code code as follows:
Public interface Teacher {
Public iterator createiterator (); Named
}
2, the specific teacher(Concreteteacher) class is the implementation of the teacher (Teacher) interface:
Copy Code code as follows:
public class Concreteteacher implements teacher{
Private object[] present = {"John came", "Dick Came", "Harry did not Come"}; Student Attendance Collection
Public iterator Createiterator () {
Return to New Concreteiterator (this); The new Roll Call
}
Public Object getelement (int index) {//Get current student's attendance status
if (index<present.length) {
return Present[index];
}
else{
return null;
}
}
public int GetSize () {
return present.length; Get the size of the student attendance set, which means you know how many people are in the class.
}
}
3, the definition of roll(iterator) interface class:
Copy Code code as follows:
Public interface Iterator {
void A (); First one
void Next (); Next
Boolean Isdone (); is the roll-call completed
Object CurrentItem (); Attendance of current classmates
}
4, the specific roll callThe (Concreteiterator) class is an implementation of the naming (iterator) interface:
Copy Code code as follows:
public class Concreteiterator implements iterator{
Private Concreteteacher teacher;
private int index = 0;
private int size = 0;
Public Concreteiterator (Concreteteacher teacher) {
This.teacher = teacher;
Size = Teacher.getsize (); Get the number of classmates
index = 0;
}
public void Primary () {//First
index = 0;
}
public void Next () {//Next
if (index<size) {
index++;
}
}
public Boolean Isdone () {//whether the roll-call has been completed
return (index>=size);
}
Public Object CurrentItem () {//Current student Attendance
Return teacher.getelement (index);
}
}
5, Write test class :
Copy Code code as follows:
public class Test {
Private iterator it;
Private Teacher Teacher = new Concreteteacher ();
public void operation () {
it = Teacher.createiterator (); The teacher started the roll call.
while (!it.isdone ()) {//If not finished
System.out.println (It.currentitem (). toString ()); Get the point of being a classmate
It.next (); Point Next
}
}
public static void Main (String agrs[]) {
Test test = new test ();
Test.operation ();
}
}
6. Description :
A: definition: The iterator mode can sequentially access elements of a cluster without exposing the aggregated internal situation.
B: In this case, the teacher (Teacher) gives the interface to create a naming (iterator) object, and the naming (iterator) defines the interface needed to traverse the student's attendance.
The advantage of the C:iterator model is that when there is a change in the (Concreteteacher) object, such as having a new classmate in the class attendance collection, or reducing the class, this change has no effect on the client.
