jdk1.6 1.7 list扩容的区别

jdk1.6

public void ensureCapacity(int minCapacity) {

modCount++;

int oldCapacity = elementData.length;

if (minCapacity > oldCapacity) {

Object oldData[] = elementData;

int newCapacity = (oldCapacity * 3)/2 + 1;

if (newCapacity < minCapacity)

newCapacity = minCapacity;

// minCapacity is usually close to size, so this is a win:

elementData = Arrays.copyOf(elementData, newCapacity);

jdk1.7

private void grow(int minCapacity) {
// overflow-conscious code
int oldCapacity = elementData.length;
int newCapacity = oldCapacity + (oldCapacity >> 1);
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);
}

private static int hugeCapacity(int minCapacity) {
if (minCapacity < 0) // overflow
throw new OutOfMemoryError();
return (minCapacity > MAX_ARRAY_SIZE) ?
Integer.MAX_VALUE :
MAX_ARRAY_SIZE;
}

区别：1、扩容后大小区别，1.6乘除运算后为1.5x+1，1.7位运算后为1.5x，效率提高

2、1.7设置最大容量限制