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public interface StudentIterator {
    boolean hasNext();
    Student next();
}
public static class StudentIteratorImpl implements StudentIterator {
    private final List<Student> list;
    private int position = 0;
    public StudentIteratorImpl(List<Student> list) {
        this.list = list;
    }
    @Override
    public boolean hasNext() {
        return position < list.size();
    }
    @Override
    public Student next() {
        return list.get(position++);
    }
}

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public interface StudentAggregate {
    void addStudent(Student student);
    void removeStudent(Student student);
    StudentIterator getStudentIterator();
}
public static class StudentAggregateImpl implements StudentAggregate {
    private final List<Student> list = new ArrayList<>();
    @Override
    public void addStudent(Student student) {
        this.list.add(student);
    }
    @Override
    public void removeStudent(Student student) {
        this.list.remove(student);
    }
    @Override
    public StudentIterator getStudentIterator() {
        return new StudentIteratorImpl(list);
    }
}

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@Data
@AllArgsConstructor
@NoArgsConstructor
public static class Student {
    private String name;
    private String number;
}

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StudentAggregate aggregate = new StudentAggregateImpl();
aggregate.addStudent(new Student("张三", "001"));
        aggregate.addStudent(new Student("李四", "002"));
        aggregate.addStudent(new Student("王五", "003"));
        aggregate.addStudent(new Student("赵六", "004"));

StudentIterator iterator = aggregate.getStudentIterator();
while (iterator.hasNext()) {
Student student = iterator.next();
    System.out.println(student);
}

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a20_迭代器模式.Student(name=张三, number=001)
a20_迭代器模式.Student(name=李四, number=002)
a20_迭代器模式.Student(name=王五, number=003)
a20_迭代器模式.Student(name=赵六, number=004)