自定義一個動態陣列類，陣列只有在增加元素時才會增加大小，節約空間，適用於修改少、遍歷多的操作。

package list;


public class DyList<T> {
	private Object[] elements = null;
	public DyList(){
		elements = new Object[0];
	}
	public DyList(int size){
		if (size > 0){
			elements = new Object[size];
		}else{
			elements = new Object[0];
		}
		
	}
	public void add(T i){
		Object[] tmp = new Object[elements.length+1];
		System.arraycopy(elements, 0, tmp, 0, elements.length);
		
		tmp[elements.length] = i;
		
		elements = tmp;
	}
	@SuppressWarnings("unchecked")
	public T get(int index){
		return (T)elements[index];
	}
	public int size(){
		return elements.length;
	}