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private void grow(int minCapacity) {        // overflow-conscious code        int oldCapacity = elementData.length;        int newCapacity = oldCapacity + (oldCapacity >> 1); //扩容长度计算        if (newCapacity - minCapacity < 0)            newCapacity = minCapacity;        if (newCapacity - MAX_ARRAY_SIZE > 0)            newCapacity = hugeCapacity(minCapacity);        // minCapacity is usually close to size, so this is a win:        elementData = Arrays.copyOf(elementData, newCapacity);    }

contains:

public boolean contains(Object o) {   return indexOf(o) >= 0;}public int indexOf(Object o) {   if (o == null) {      for (int i = 0; i < size; i++)         if (elementData[i]==null)            return i;   } else {      for (int i = 0; i < size; i++)        if (o.equals(elementData[i])) //注意点：自己的对象是否实现了equals           return i;   }   return -1;}

删除元素remove

 1.按index方式删除

public E remove(int index) {        rangeCheck(index);        modCount++;        E oldValue = elementData(index);        int numMoved = size - index - 1;        if (numMoved > 0)            System.arraycopy(elementData, index+1, elementData, index,                             numMoved); //注意删除的方式是数组往前移 所以便利删除不从新计算下标会有问题        elementData[--size] = null; // clear to let GC do its work        return oldValue;    }

2.对象方式删除

public boolean remove(Object o) {        if (o == null) {            for (int index = 0; index < size; index++)                if (elementData[index] == null) {                    fastRemove(index);                    return true;                }        } else {            for (int index = 0; index < size; index++)                if (o.equals(elementData[index])) { //比较的时候equals                    // 用index方式删除                    fastRemove(index);                    return true;                }        }        return false;    }    /*     * Private remove method that skips bounds checking and does not     * return the value removed.     */    private void fastRemove(int index) {        modCount++;        int numMoved = size - index - 1;        if (numMoved > 0)            System.arraycopy(elementData, index+1, elementData, index,                             numMoved);        elementData[--size] = null; // clear to let GC do its work    }

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