iterator模式
需求：给大家举个例子，现在假设，有一个教室类，里面包含了一堆学生，我现在要遍历教室里的学生，怎么来玩儿
public interface Aggregate { public abstract Iterator iterator(); } public interface Iterator { public abstract boolean hasNext(); public abstract Object next(); } public class Student { private String name; public Student (String name) { this.name = name; } public String getName() { return name; } } public class Classroom implements Aggregate { private Student[] students; private int last = 0; public Classroom(int size) { this.students = new Student[size]; } public Student getStudents(int size) { return students[size]; } public void addStudent(Student student) { this.students[last] = student; last++; } public int getLength() { return last; } @Override public Iterator iterator() { return new ClassroomIterator(this); } } public class ClassroomIterator implements Iterator { private Classroom classroom; private int index; public ClassroomIterator(Classroom classroom) { this.classroom = classroom; this.index = 0; } @Override public boolean hasNext() { if (index < classroom.getLength()) { return true; } else { return false; } } @Override public Object next() { Student student=classroom.getStudents(index); index++; return student; } } public class Main { public static void main(String[] args) { Classroom classroom = new Classroom(2); classroom.addStudent(new Student("小李")); classroom.addStudent(new Student("王三")); Iterator iterator = classroom.iterator(); while (iterator.hasNext()){ System.out.println(((Student)iterator.next()).getName()); } } }
面向Iterator接口编程，无论底层的数据结构和迭代算法如何变化，调用者都不用修改代码
高内聚，低耦合，漂亮
其实一般很少自己写这个iterator模式的，一般都是在集合编程中使用，尤其是如果要对集合元素遍历过程中做插入删除操作，那就用iterator，体验JDK已经封装好的iterator模式，加深印象，如果要对某个类中的集合进行遍历，由那个集合类返回一个iterator回来，我们统一面向iterator迭代器接口来编程遍历，提高系统整体的可维护性，可扩展性
如果自己写iterator模式，一般是研发底层的框架，比如提供某个数据给外部遍历，那么可以使用iterator模式自己封装迭代器，以后阶段如果有机会，我们也会去实践
