B02 迭代器模式 示例

示例类图

迭代器模式.png

示例代码

public class Course {

    private String name;

    public Course(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

}

public interface CourseAggregate {

    void addCourse(Course course);
    void removeCourse(Course course);
    CourseIterator getCourseIterator();

}

public class CourseAggregateImpl implements CourseAggregate {

    private List courseList;

    public CourseAggregateImpl() {
        this.courseList = new ArrayList();
    }

    @Override
    public void addCourse(Course course) {
        courseList.add(course);
    }

    @Override
    public void removeCourse(Course course) {
        courseList.remove(course);
    }

    @Override
    public CourseIterator getCourseIterator() {
        return new CourseIteratorImpl(courseList);
    }

}

public interface CourseIterator {
    Course nextCourse();
    boolean isLastCourse();
}

public class CourseIteratorImpl implements CourseIterator {

    private List courseList;
    private int position;

    public CourseIteratorImpl(List courseList){
        this.courseList = courseList;
    }

    @Override
    public Course nextCourse() {
        System.out.println("返回课程,位置是: " + position);
        return (Course)courseList.get(position ++);
    }

    @Override
    public boolean isLastCourse(){
        if(position < courseList.size()){
            return false;
        }
        return true;
    }

}

public class Test {

    public static void main(String[] args) {

        Course course1 = new Course("Java电商一期");
        Course course2 = new Course("Java电商二期");
        Course course3 = new Course("Java设计模式精讲");
        Course course4 = new Course("Python课程");
        Course course5 = new Course("算法课程");
        Course course6 = new Course("前端课程");


        CourseAggregate courseAggregate = new CourseAggregateImpl();

        courseAggregate.addCourse(course1);
        courseAggregate.addCourse(course2);
        courseAggregate.addCourse(course3);
        courseAggregate.addCourse(course4);
        courseAggregate.addCourse(course5);
        courseAggregate.addCourse(course6);

        System.out.println("-----课程列表-----");
        printCourses(courseAggregate);

        courseAggregate.removeCourse(course4);
        courseAggregate.removeCourse(course5);

        System.out.println("-----删除操作之后的课程列表-----");
        printCourses(courseAggregate);
    }

    public static void printCourses(CourseAggregate courseAggregate){
        CourseIterator courseIterator = courseAggregate.getCourseIterator();
        while(!courseIterator.isLastCourse()){
            Course course = courseIterator.nextCourse();
            System.out.println(course.getName());
        }
    }

}

输出：

-----课程列表-----
返回课程,位置是: 0
Java电商一期
返回课程,位置是: 1
Java电商二期
返回课程,位置是: 2
Java设计模式精讲
返回课程,位置是: 3
Python课程
返回课程,位置是: 4
算法课程
返回课程,位置是: 5
前端课程
-----删除操作之后的课程列表-----
返回课程,位置是: 0
Java电商一期
返回课程,位置是: 1
Java电商二期
返回课程,位置是: 2
Java设计模式精讲
返回课程,位置是: 3
前端课程