Java-创建自定义ArrayList

/**
* 自己实现一个ArrayList，帮助自己更好地理解ArrayLIst类的底层结构
*/
public class MyArrayList /*implements List*/ {
private Object[] elementData;
private int size;

public int getSize() {
    return size;
}

public boolean isEmpty() {
    return size == 0;
}

public MyArrayList() {
    this(10);
}

public MyArrayList(int initialCapacity) {
    try {
        if (initialCapacity < 0) {
            throw new Exception();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    elementData = new Object[initialCapacity];
}

public void add(Object obj) {
    //实现数组扩容
    ensureCapacity();
    elementData[size++] = obj;
    /*size++;*/
}

public Object get(int index) {
    rangeCheck(index);
    return elementData[index];
}

public void remove(int index) {
    //删除指定位置的对象
    rangeCheck(index);
    int numMoved = size - index - 1;
    System.arraycopy(elementData, index + 1, elementData, index,
            numMoved);
    elementData[--size] = null;
}

public void remove(Object obj) {
    for (int i = 0; i < size; i++) {
        if (get(i).equals(obj)) {
            remove(i);
        }
    }
}

public Object set(int index, Object obj) {
    rangeCheck(index);
    Object oldValue = elementData[index];
    elementData[index] = obj;
    return oldValue;
}

public void add(int index, Object obj) {
    rangeCheck(index);
    ensureCapacity();
    System.arraycopy(elementData, index, elementData, index + 1, size - index);
    elementData[index] = obj;
    size++;
}

private void rangeCheck(int index) {
    if (index < 0 || index >= size) {
        try {
            throw new Exception();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

private void ensureCapacity() {
    if (size == elementData.length) {
        Object[] newArray = new Object[size * 2 + 1];
        System.arraycopy(elementData, 0, newArray, 0, elementData.length);
        elementData = newArray;
    }
}

public static void main(String[] args) {
    MyArrayList list = new MyArrayList(3);
    System.out.println(list.getSize());
    if (list.isEmpty()) {
        System.out.println("数组是空的");
    }

    list.add("aaa");
    list.add("bbb");
    list.add("ccc");
    list.add("ddd");
    System.out.println(list.getSize());
    System.out.println(list.isEmpty());
    System.out.println(list.get(3));

    list.remove(3);
    System.out.println(list.getSize());

}
}