模拟容器的Iterator实现，让自己的类能够使用for-each

继承AbstractCollection并重写iterator和size方法能创造出迭代器

实现Iterable接口能使迭代器有for-each功能

import java.util.AbstractCollection;
import java.util.Iterator;

public class PersonIterator extends AbstractCollection<Person> implements Iterable<Person>{
	
	Person persons[];
	int index = 0;
	int count = 0;
	
	public PersonIterator(int size) {
		persons = new Person[size];
	}
	
	public boolean add(Person p) {
		if(index >= persons.length) {
			return false;
		} else {
			persons[index ++] = p;
			count ++;
			return true;
		}
	}
	@Override
	public Iterator<Person> iterator() {
		return new Iterator<Person>() {
			int index = 0;//Iterator的索引
			
			@Override
			public boolean hasNext() {
				if(index < count) {
					return true;
				} else {
					return false;
				}
			}

			@Override
			public Person next() {
				return persons[index ++];
			}

			@Override
			public void remove() {
				
			}
		};
	}

	@Override
	public int size() {
		return count;
	}
	
}

class Person {
	String name;
	int age;
	public Person(String name,int age) {
		this.name = name;
		this.age = age;
	}
	public String toString() {
		return this.name + " " + this.age;
	}
}

public class TestPersonIterator {
	public static void main(String[] args) {
		Person p1 = new Person("aa",11);
		Person p2 = new Person("bb",11);
		Person p3 = new Person("cc",11);
		Person p4 = new Person("dd",11);
		Person p5 = new Person("ee",11);
		
		PersonIterator pi = new PersonIterator(5);
		
		pi.add(p1);
		pi.add(p2);
		pi.add(p3);
		pi.add(p4);
		pi.add(p5);
		
		for(Person p : pi.persons) {
			System.out.print("[" + p + "]   ");
		}
		
	}
}

//output 
[aa 11]   [bb 11]   [cc 11]   [dd 11]   [ee 11]