Java 中的 String.split(" ") 是否预先完成所有工作？

Question

Say I have a very long String called str , and I'm looking for the first instance of "hello" . For now we can say each token is separated by a space, but in the more complex case it won't be, hence the use of split rather than StringTokenizer. Now, let's also say "hello" is only the third word in the String. Is the following algorithm O(n) or O(1) ?

for (String word : str.split(" ") )
    if ( word.equals("hello") ) return;

Answer 1

It would be O(1) if it does not matter how many tokens you have in your array, which is not true. It is O(n) .