Java Split函数极诡异问题

//String[] ss = "".split(""); //results:[""]
//String[] ss = "".split("a"); //results:[""]
//String[] ss = "a".split(""); //results:["","a"]
//String[] ss = "a".split("a"); //results:[]
//String[] ss = "a".split("aa"); //results:["a"]
//String[] ss = "aa".split(""); //results:["","a","a"]
//String[] ss = "aa".split("a"); //results:[]
//String[] ss = "aa".split("aa"); //results:[]