JAVA15——手动实现迭代器

手动实现迭代器

一、实现迭代器中的hasNext和next方法：

/**
 * 简化迭代器原理
 * hasNext
 * next
 * @author qiao39gs
 *
 */
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 hasNest(){
		return cursor+1<size;
	}
	/**
	 * 获取下一个元素
	 * @return
	 */
	public String next(){
		cursor++;	//移动一次
		return elem[cursor];
	}
	//删除元素
	public void remove(){
	}
	
	public static void main(String[] args) {
		MyArrayList list = new MyArrayList();
		while(list.hasNest()){
			System.out.println(list.next());
		}
	}
	
}

二、加入接口 提供方法：

import java.util.Iterator;

/**
 * 简化迭代器原理 加入接口 提供方法
 * hasNext
 * next
 * @author qiao39gs
 *
 */
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
		 * @return
		 */
		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();
	}
	
	public static void main(String[] args) {
		MyArrayList2 list = new MyArrayList2();
		Iterator<String> it = list.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
		}
	}
	
}

三、创建匿名内部类

 import java.util.Iterator;

/**
 * 简化迭代器原理 加入接口 提供方法
 * hasNext
 * next
 * @author qiao39gs
 *
 */
public class MyArrayList3 {
	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
			 * @return
			 */
			public String next(){
				cursor++;	//移动一次
				return elem[cursor];
			}
			//删除元素
			public void remove(){
				//没有实现
			}
		};
	}
	
	public static void main(String[] args) {
		MyArrayList3 list = new MyArrayList3();
		Iterator<String> it = list.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
		}
	}
	
}

四、实现for的迭代器

import java.util.Iterator;

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
			 * @return
			 */
			public String next(){
				cursor++;	//移动一次
				return elem[cursor];
			}
			//删除元素
			public void remove(){
				//没有实现
			}
		};
	}
	
	public static void main(String[] args) {
		MyArrayList3 list = new MyArrayList3();
		Iterator<String> it = list.iterator();
		while(it.hasNext()){
			System.out.println(it.next());
		}
		//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);
		}
	}
	
}