求详解ViewerSorter接口

[yongger520]

Useful APIs defined by ViewerSorter include:

category(Object) Returns the category of the given element.
compare(Viewer, Object, Object) Returns a negative, zero, or positive number depending on whether the first element is less than, equal to, or greater than the second element.

getCollator() Returns the collator used to sort strings.

isSorterProperty(Object, String)
Returns whether this viewer sorter would be affected by a change to the given property of the given element.

sort(Viewer viewer, Object[])
Sorts the given elements in place, modifying the given array
前两方法不用介绍，后三个方法哪位能介绍下，最后给例子，不知道具体作用是什么