JDK1.7 environment
1, configuration parameters
ArrayList()
ArrayList (int initialCapacity) with the specified size to initialize internal array
ArrayList (Collection <? Extends E> c) with a construct ICollection object, and the set of elements to ArrayList
2、ArrayList()
ArrayList list = new ArrayList<String>();
Summary: The initial capacity of the array 10 , each expansion by copeOf manner, after the capacity of the original 1.5 times
Source:
ElementData just an empty object array initialized array of objects.
elementData: buffer storage array ArrayList elements. ArrayList capacity is the length of this array buffer. So in this case ArrayList capacity is 0;
When performing List.add () method, ArrayList initialization only the size of the array capacity
When the first call to add (), elementData == EMPTY_ELEMENTDATA will be equal, and the value is an empty array.
The first call minCapacity = 1,
The value is a value acquired DEFAULT_CAPACITY; minCapacity = Math.max (DEFAULT_CAPACITY, minCapacity)
In ensureExplicitCapacity method, first add () method, this time minCapacity = 10, elementData.length = 1,
So it will not enter the grow () method.
When minCapacity greater than 10, performs Grow () calculated for expansion,
E.g:
When added to the first element of the array 11, the array 15 of expanded capacity.
int newCapacity = 10 + (10 >> 1) = 15
When added to the first element of the array 16, the array 22 of expanded capacity.
int newCapacity = 15+ (15>> 1) = 22
