设计模式【15】| 迭代子模式

 就是一个迭代器，用来遍历集合。java 原生代码中的迭代器也是采用这种模式

1.程序设计

出于更深入的了解java迭代器原理，自己写一遍还是有必要的。

       程序设计：两个接口，两个实现类。

       集合接口：构造集合的存储结构

       迭代器接口：用来对集合进行遍历。

       自己定义一个User的model ，自定义集合，并定义添加item的方法，然后通过自己定义的迭代器，对其进行遍历。是不是很溜呀。那我们开始吧。这个弯子有点大，多看几遍就明白了。

集合接口： NotTrueCollection

package com.cn.iteractor;

public interface NotTrueCollection<T> {

	NotTrueIteractor<T> createIteractor();

	Object get(int i);

	int size();

	void addItem(T t);

	void deleteItem(T t);

}　

迭代器接口： NotTrueIteractor

package com.cn.iteractor;

public interface NotTrueIteractor<T> {
	
	boolean hasNext();

	Object getPrevious();

	Object next();

	Object getFirst();

	Object getLasst();
}

集合实现类：MyCollection

package com.cn.iteractor;

public class MyCollection<T> implements NotTrueCollection<T> {

    private Object[] collections = new Object[1];

    private int index = 0;

    @Override
    public NotTrueIteractor<T> createIteractor() {
        return new MyIteractor<T>(this);
    }

    @Override
    public Object get(int i) {
        return collections[i];
    }

    @Override
    public int size() {
        return collections.length;
    }

    @Override
    public void addItem(T t) {
        int lengths = size();
        if (index >= size()) {
            Object[] collectionTemp = collections;
            collections = new Object[lengths + 1];
            for (int i = 0; i < collectionTemp.length; i++) {
                collections[i] = collectionTemp[i];
            }
            collections[lengths] = t;
        } else {
            collections[lengths-1] = t;
        }
        index++;
    }

    @Override
    public void deleteItem(T t) {
        // TODO Auto-generated method stub

    }

}

迭代器实现类 MyIteractorimplements

package com.cn.iteractor;

public class MyIteractor<T> implements NotTrueIteractor<T> {

    private NotTrueCollection<T> notTrueCollectin;

    private int post = -1;

    public MyIteractor(NotTrueCollection<T> notTrueCollectin) {
        this.notTrueCollectin = notTrueCollectin;
    }

    @Override
    public boolean hasNext() {
        if (post < notTrueCollectin.size() - 1) {
            return true;
        }
        return false;
    }

    @Override
    public Object getPrevious() {
        if (post > 0) {
            post--;
        }
        return notTrueCollectin.get(post);
    }

    @Override
    public Object next() {
        if (post < notTrueCollectin.size() - 1) {
            post++;
        }
        return notTrueCollectin.get(post);
    }

    @Override
    public Object getFirst() {
        return notTrueCollectin.get(0);
    }

    @Override
    public Object getLasst() {
        return notTrueCollectin.get(notTrueCollectin.size() - 1);
    }
    
}

测试类： User

package com.cn.iteractor;

public class User {

    private String name;
    private String sex;
    private int age;
    private String address;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User [name=" + name + ", sex=" + sex + ", age=" + age + ", address=" + address + "]";
    }

}

测试结果：Test

package com.cn.iteractor;

public class Test {

    public static void main(String[] args) {
        NotTrueCollection<User> myCollection = new MyCollection<>();
        User user1 = new User();
        User user2 = new User();
        User user3 = new User();
        user1.setName("Harvey");
        user2.setName("Tom");
        user3.setName("Jack");
        myCollection.addItem(user1);
        myCollection.addItem(user2);
        myCollection.addItem(user3);
        NotTrueIteractor<User> iteractor = myCollection.createIteractor();
        while (iteractor.hasNext()) {
            User users = (User) iteractor.next();
            System.out.println(users);
        }

    }
}

       说明：代码中User模型省略了getset还有toString()方法。另外遍历似乎只有在遍历集合的时候才需要，但是java 原生的代码已经将集合遍历完美的实现，我们只要理解其原理就行了。