首先看这两类都实现List接口，而List接口一共有三个实现类，分别是ArrayList、Vector和LinkedList。List用于存放多个元素，能够维护元素的次序，并且允许元素的重复。3个具体实现类的相关区别如下：
1 public boolean add(E e) {
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3 ensureCapacity(size + 1); // 增加元素，判断是否能够容纳。不能的话就要新建数组
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5 elementData[size++] = e;
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7 return true;
8
9 }
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11 public void ensureCapacity(int minCapacity) {
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13 modCount++;
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15 int oldCapacity = elementData.length;
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17 if (minCapacity > oldCapacity) {
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19 Object oldData[] = elementData; // 此行没看出来用处，不知道开发者出于什么考虑
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21 int newCapacity = (oldCapacity * 3)/2 + 1; // 增加新的数组的大小
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23 if (newCapacity < minCapacity)
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25 newCapacity = minCapacity;
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27 // minCapacity is usually close to size, so this is a win:
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29 elementData = Arrays.copyOf(elementData, newCapacity);
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31 }
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33 }
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35
1 private void ensureCapacityHelper(int minCapacity) {
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3 int oldCapacity = elementData.length;
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5 if (minCapacity > oldCapacity) {
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7 Object[] oldData = elementData;
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9 int newCapacity = (capacityIncrement > 0) ?
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11 (oldCapacity + capacityIncrement) : (oldCapacity * 2);
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13 if (newCapacity < minCapacity) {
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15 newCapacity = minCapacity;
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17 }
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19 elementData = Arrays.copyOf(elementData, newCapacity);
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21 }
22
23 }
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25