Java中AyyarList类的基本实现_ayylist

/**
 * 自己实现一个ArrayList，帮助我们更好地理解ArrayList类的底层结构
 * @author Administrator
 *
 */
public class MyArrayList {
 
	private Object[] elementData;
	private int size;
	
	public MyArrayList(){
		this(10); //默认的数组长度为10
	}
	
	public MyArrayList(int initialCapacity){
		if(initialCapacity<0)
			try {
				throw new Exception();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		elementData = new Object[initialCapacity];	
	}	
	
	public int size(){
		return size;
	}
	
	public void ensureCapacity(){
		//若数组已满，则给数组扩容
		if(size==elementData.length){
			Object[] newArray = new Object[size*2];
			System.arraycopy(elementData, 0, newArray, 0, elementData.length);
			elementData = newArray;
		}
	}
	
	public void add(Object o){
		ensureCapacity();
		elementData[size]=o;
		size++;
	}
	
	public void add(int index, Object obj){
		rangeCheck(index);
		ensureCapacity();
		for(int i=size-1;i>=index;i--){
			elementData[i+1]=elementData[i];
		}
		elementData[index]=obj;
		size++;
	}
	
	public boolean isEmpty(){
		return size==0;
	}
	
	
	public Object get(int index){
		rangeCheck(index);
		return elementData[index];
	}
	
	public Object remove(int index){
		rangeCheck(index);
		Object deletedObject = elementData[index];
		//int numMoved = size-index-1;
		//System.arraycopy(elementData, index+1, elementData, index, numMoved);
		for(int i=index+1; i<this.size();i++){
			elementData[i-1]=elementData[i];
		}
		elementData[--size]=null;
		return deletedObject;
	}
	
	public boolean remove(Object obj){
		for(int i=0; i<this.size();i++){
			if(elementData[i].equals(obj)){
				remove(i);
				return true;
			}
		}
		return false;
	}
	
	public Object set(int index, Object obj){
		rangeCheck(index);
		Object oldValue=elementData[index];
		elementData[index]=obj;
		return oldValue;
	}
	
	private void rangeCheck(int index){
		if( index < 0 ||index >= size){
			try {
				throw new Exception();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
	
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
			MyArrayList list = new MyArrayList(3);
			list.add(123);
			list.add("haha");
			list.add("wxxyy");
			list.add("you");
			System.out.println(list.get(3));
	}
 
}