树上这样写的Optionally, you can specify where in the main string the hould begin—but the returned value is always relative to the very first characsearch ster of the main string.
就是说第2个可选参数决定了搜索的起始位置,那么
"012345".indexOf("3",4)的结果是3,不应该啊,因为搜索是从4开始的,怎么会搜索到3呢??请教各位高手