Map map = new HashMap();
　　Iterator iter = map.entrySet().iterator();
　　while (iter.hasNext()) {
　　Map.Entry entry = (Map.Entry) iter.next();
　　Object key = entry.getKey();
　　Object val = entry.getValue();
　　}

　Map map = new HashMap();
　　Iterator iter = map.keySet().iterator();
　　while (iter.hasNext()) {
　　Object key = iter.next();
　　Object val = map.get(key);
　　}

/** 
 * 手写ArrayList  
 */  
public class MyArrayList{  
  
  
    private Object[] value = null;  
  
    private int size = 0;  
  
    MyArrayList() {  
        value = new Object[10];  
    }  
  
  
    public boolean add(Object obj){  
        if(size == value.length)  
            expansion();  
        value[size++]=obj;  
        return true;  
    }  
  
  
    public Object get(int index){  
        return value[index];  
    }  
  
    public void remove(Object obj){  
        Object[] obj2 = new Object[size];  
        int index = 0;  
        int id = 0;  
        for (int i = 0; i <= size; i++) {  
            if(!(value[i].toString().equals(obj.toString()))){  
                obj2[index] = value[i];  
                index ++;  
            }else{  
                id ++ ;  
                if(id == 1)  
                    size --;  
                else{  
                    obj2[index] = value[i];  
                    index ++;  
                }  
            }  
        }  
        value = obj2;  
    }  
  
    @SuppressWarnings("null")  
    public void set(int index,Object obj){  
        Object[] newObj = new Object[size];;  
        for (int i = 0; i < size; i++) {  
            if(i == index)  
                newObj[i] = obj;  
            else  
                newObj[i] = value[i];  
        }  
        value = newObj;  
    }  
  
    public int size(){  
        return size;  
    }  
  
    private boolean expansion() {  
        Object[] temp = new Object[value.length + 5];  
        temp = value.clone();  
        /** 
        * 注意：clone只对一维数组起作用，而不能用于二维数组， 因为java没有二维数组的概念，而只有数组的数组，二维 
        * 数组存储的是几个一维数组的引用，而使用clone也只是 拷贝了这几个引用，说白了还是原来那几个一维数组对象。 
        * 如果想用于二维数组，那么就遍历其中的一维数组，挨个 拷贝一维数组到目标二维数组中的一维数组下。 
        */  
        value = temp;  
        return true;  
    }  
  
  
    public void clear(){  
        size = 0;  
        value = null;  
    }  
  
    public static void main(String[] args) {  
        MyArrayList ma = new MyArrayList();  
        ma.add("hello");  
        ma.add("world");  
        ma.add("java");  
        System.out.println(ma.get(1));  
        System.out.println(ma.size());  
        ma.set(1, "new");  
        System.out.println(ma.get(1));  
        System.out.println(ma.size());  
    }  
  
}

public class MyLinkedList<AnyType> {
    private static class Node<AnyType>{
        public AnyType data;
        public Node<AnyType> prev;
        public Node<AnyType> next;
        public Node(AnyType d, Node<AnyType> p, Node<AnyType> n){
            data = d;
            prev = p;
            next = n;
        }
    }

    private int theSize;
    private int modCount;
    private Node<AnyType> beginMarker;
    private Node<AnyType> endMarker;

    public MyLinkedList(){
        clear();
    }

    public void clear(){
        beginMarker = new Node<AnyType>(null, null, null);
        endMarker = new Node<AnyType>(null, beginMarker, null);
        beginMarker.next = endMarker;
        theSize = 0;
    }

    public int size(){
        return theSize;
    }
    public boolean add(AnyType x){
        add(size(), x);
        return true;
    }

    public void add(int idx, AnyType x){
        addBefore(getNode(idx), x);
    }

    public AnyType get(int idx){
        return getNode(idx).data;
    }

    private void addBefore(Node<AnyType> p, AnyType x){
        Node<AnyType> newNode = new Node<AnyType>(x, p.prev, p);
        newNode.prev.next = newNode;
        p.prev = newNode;
        theSize++;
        modCount++;
    }

    private Node<AnyType> getNode(int idx){
        Node<AnyType> p;

        if(idx < 0 || idx > size()){
            System.out.println("IndexOutOfBoundsException");
        }

        if(idx <= size()/2){
            System.out.println(idx);
            p = beginMarker.next;
            for(int i = 0; i < idx; i++){
                p = p.next;
            }
        }else{
            p = endMarker;
            for(int i = size(); i > idx; i--){
                p = p.prev;
            }
        }

        return p;

    }

    public boolean find(AnyType x){
        Node<AnyType> p = beginMarker.next;
        for(int i = 0; i < size(); i++){
            if(p.data == x){
                return true;
            }
            p = p.next;
        }
        return false;
    }


    public String toString(){
        String s = "";
        Node<AnyType> p = beginMarker.next;
        for(int i = 0; i < size(); i++){
            s += p.data +",";
            p = p.next;
        }
        return s;
    }


}