javase 自定义迭代器

1 定义基本类方式实现迭代器 ：

/**
 * 简化迭代器原理
 * hasNext
 * next
 * @author Administrator
 *
 */
public class MyArrayList {
	private String[] elem ={"a","b","c","d","e","f","g"};
	private int size = elem.length;
	
	
	private int cursor =-1;
	/**
	 * 判断是否存在下一个元素
	 * @return
	 */
	public boolean hasNext(){		
		return cursor+1<size;
	}
	/**
	 * 获取下一个元素
	 */
	public String next(){
		cursor++; //移动一次
		return elem[cursor];
	}
	/**
	 * 删除元素
	 */
	public void remove(){
		
	}
	
	
	
	/**
	 * @param args
	 */
	public static void main(String[] args) { // 只能使用这个对象一次
		MyArrayList list = new MyArrayList();
		while(list.hasNext()){
			System.out.println(list.next());
		}
		
		list = new MyArrayList();
		while(list.hasNext()){
			System.out.println(list.next());
		}
	}

}

2 包装基本类，实现基本类提供的迭代器能够被多次调用 

/**
 * 简化迭代器原理 加入接口 提供方法
 * hasNext
 * next
 * @author Administrator
 *
 */
public class MyArrayList2 {
	private String[] elem ={"a","b","c","d","e","f","g"};
	private int size = elem.length;
	
	
	private class MyIt implements Iterator<String>{
		private int cursor =-1;
		/**
		 * 判断是否存在下一个元素
		 * @return
		 */
		public boolean hasNext(){		
			return cursor+1<size;
		}
		/**
		 * 获取下一个元素
		 */
		public String next(){
			cursor++; //移动一次
			return elem[cursor];
		}
		/**
		 * 删除元素
		 */
		public void remove(){
			//没有实现
		}
	
	}
	
	public Iterator<String> iterator(){
		return new MyIt();
	}
	
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		MyArrayList2 list = new MyArrayList2(); // 把对象包装起来，在调用函数中不断的new出新对象，cursor不断的从-1开始，实现多次调用
		Iterator<String> it =list.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
		}
		
		
		it =list.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
		}
		
	}

}

3  使用匿名内部类 包装迭代器 ：

public class MyArrayList3 implements java.lang.Iterable<String> {
	private String[] elem ={"a","b","c","d","e","f","g"};
	private int size = elem.length;
	
	
	/**
	 * 匿名内部类
	 * @return
	 */	
	public Iterator<String> iterator(){ 
		return new Iterator<String>(){
			private int cursor =-1;
			/**
			 * 判断是否存在下一个元素
			 * @return
			 */
			public boolean hasNext(){		
				return cursor+1<size;
			}
			/**
			 * 获取下一个元素
			 */
			public String next(){
				cursor++; //移动一次
				return elem[cursor];
			}
			/**
			 * 删除元素
			 */
			public void remove(){
				//没有实现
			}
		
		};
	}
	
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		MyArrayList3 list = new MyArrayList3();
		Iterator<String> it =list.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
			it.remove(); //删除元素
		}
		
		
		it =list.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
		}
		System.out.println("增强for，必须实现java.lang.Iterable接口，重写iterator方法");
		for(String temp:list){
			System.out.println(temp);
			
		}
		
		
		
		
		
	}

}