二十三种设计模式(java版)之Iterator

元素：

1、Interator（迭代器）

提供访问和遍历元素的接口。一般包含hasNext和next方法。

2、ConcreteInterator(具体迭代器)

实现迭代器的接口，其中包含容器的实例，以遍历其中具体的元素，其中还需要有标记当前元素位置的变量。

3、Aggregate（聚合）

提供获取容器迭代器的接口函数。

4、ConcreteAggregate(具体聚合)

实现获取容器迭代器的接口，它其实就是被遍历的容器。

类图：

代码示例：

Aggregate.java

package Interface;public interface Aggregate {public abstract Iterator iterator();}

Iterator.java

public interface Iterator {public abstract boolean hasNext();public abstract Object next();}

Student.java

public class Student {private String name = "";public Student(String name){this.name = name;}public String getName(){return this.name;}}

ClassRoom.java

public class ClassRoom implements Aggregate{private Student[] students;private int last = 0;private int maxsize;public ClassRoom(int maxsize){this.students = new Student[maxsize];this.maxsize = maxsize;}public Student getStudentAt(int index){return students[index];}public void addStudent(Student stu){if(last<maxsize){this.students[last] = stu;last++;}elseSystem.out.println("max");}public int getSize(){return this.maxsize;}@Overridepublic Iterator iterator() {// TODO Auto-generated method stubreturn new ClassRoomIterator(this);}}

ClassRoomIterator.java

public class ClassRoomIterator implements Iterator{private ClassRoom classroom;private int index;public ClassRoomIterator(ClassRoom cr){this.classroom = cr;this.index = 0;}@Overridepublic boolean hasNext() {// TODO Auto-generated method stubif(index<this.classroom.getSize())return true;elsereturn false;}@Overridepublic Object next() {// TODO Auto-generated method stubStudent stu = this.classroom.getStudentAt(index);index++;return stu;}}

Main.java

public class Main {public static void main(String[] args){ClassRoom cr = new ClassRoom(4);cr.addStudent(new Student("a"));cr.addStudent(new Student("b"));cr.addStudent(new Student("c"));cr.addStudent(new Student("d"));Iterator it = cr.iterator();while(it.hasNext()){Student stu = (Student)it.next();System.out.println(stu.getName());}}}