public void push(E item)
public E pop()
public boolean empty()
public E peek()//获得栈顶数据
public int search(Oject data)//查找栈是否有data项，没有返回-1

public void put(Key k,Value v)//加入
public void clear()//清空散列映射
public boolean containsKey(Object Key)//是否有这个Key值
public boolean containsObject(Objext Values)//是否有这个Values值
public Value get(Key k)//输入Key返回值
public Key get(Valut v)//输入值返回Key
public V remove(Key k)//
public int size()

        Collection<Student> a=hashMap1.values();//加这句（Collection没有s
        Iterator iterator1=a.iterator();