容器遍历之迭代器的使用

一个简单的main函数demo来记录下：

public static void main(String args[]){        ArrayList<Integer>list=new ArrayList<>();        list.add(1);        list.add(2);        list.add(3);        list.add(4);       for(Iterator<Integer> it=list.iterator();it.hasNext();){           int tmp=it.next();           System.out.println(tmp);       }        HashMap<String,String>map=new HashMap<>();        map.put("语文","90");        map.put("数学","80");        map.put("英语","100");        Set<String>keys=map.keySet();        for(Iterator<String>it=keys.iterator();it.hasNext();){            String tmp=it.next();            System.out.println("key is "+tmp);            System.out.println("value is "+map.get(tmp));        }          Set<Map.Entry<String,String>> enter=map.entrySet();        for(Iterator it=enter.iterator();it.hasNext();){            System.out.println(it.next());        }    }