迭代器模式

src/main/java/top/fjy8018/designpattern/pattern/behavior/iterator/Course.java

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+package top.fjy8018.designpattern.pattern.behavior.iterator;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+/**
+ * @author F嘉阳
+ * @date 2020/3/4 14:49
+ */
+@AllArgsConstructor
+@Getter
+public class Course {
+
+    private String name;
+
+}

src/main/java/top/fjy8018/designpattern/pattern/behavior/iterator/CourseAggregate.java

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+package top.fjy8018.designpattern.pattern.behavior.iterator;
+
+/**
+ * 对课程进行处理
+ *
+ * @author F嘉阳
+ * @date 2020/3/4 14:48
+ */
+public interface CourseAggregate {
+
+    void addCourse(Course course);
+
+    void removeCourse(Course course);
+
+    /**
+     * 获取课程迭代器
+     *
+     * @return
+     */
+    CourseIterator getCourseIterator();
+}

src/main/java/top/fjy8018/designpattern/pattern/behavior/iterator/CourseAggregateImpl.java

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+package top.fjy8018.designpattern.pattern.behavior.iterator;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author F嘉阳
+ * @date 2020/3/4 14:50
+ */
+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);
+    }
+}

src/main/java/top/fjy8018/designpattern/pattern/behavior/iterator/CourseIterator.java

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+package top.fjy8018.designpattern.pattern.behavior.iterator;
+
+import java.util.ArrayList;
+
+/**
+ * JDK迭代器
+ * {@link java.util.Iterator}
+ * 集合内部类实现 {@link ArrayList.Itr#hasNext()}
+ * 同时做了进一步扩展 {@link ArrayList.ListItr}
+ * <p>
+ * mybatis中 {@link org.apache.ibatis.cursor.defaults.DefaultCursor}
+ * 其持有游标迭代器对象 {@link org.apache.ibatis.cursor.defaults.DefaultCursor.CursorIterator}
+ *
+ * @author F嘉阳
+ * @date 2020/3/4 14:49
+ */
+public interface CourseIterator {
+
+    /**
+     * 获取下一个课程
+     *
+     * @return
+     */
+    Course nextCourse();
+
+    /**
+     * 是否是最后一个课程
+     *
+     * @return
+     */
+    boolean isLastCourse();
+}

src/main/java/top/fjy8018/designpattern/pattern/behavior/iterator/CourseIteratorImpl.java

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+package top.fjy8018.designpattern.pattern.behavior.iterator;
+
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.List;
+
+/**
+ * @author F嘉阳
+ * @date 2020/3/4 14:50
+ */
+@Slf4j
+public class CourseIteratorImpl implements CourseIterator {
+
+    private List courseList;
+
+    private int position;
+
+    private Course course;
+
+    public CourseIteratorImpl(List courseList) {
+        this.courseList = courseList;
+    }
+
+    @Override
+    public Course nextCourse() {
+        log.info("返回课程,位置是: {}", position);
+        course = (Course) courseList.get(position);
+        position++;
+        return course;
+    }
+
+    @Override
+    public boolean isLastCourse() {
+        if (position < courseList.size()) {
+            return false;
+        }
+        return true;
+    }
+}

src/test/java/top/fjy8018/designpattern/pattern/behavior/iterator/CourseIteratorTest.java

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+package top.fjy8018.designpattern.pattern.behavior.iterator;
+
+import lombok.extern.slf4j.Slf4j;
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author F嘉阳
+ * @date 2020/3/4 14:52
+ */
+@Slf4j
+class CourseIteratorTest {
+
+    @Test
+    void nextCourse() {
+        Course course1 = new Course("Java分布式");
+        Course course2 = new Course("Java系统设计");
+        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);
+
+        log.info("-----课程列表-----");
+        printCourses(courseAggregate);
+
+        courseAggregate.removeCourse(course4);
+        courseAggregate.removeCourse(course5);
+
+        log.info("-----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();
+            log.info(course.getName());
+        }
+    }
+}