Java 统计字符串的长度，忽略字母的大小写

You will write an Average Word Length program that uses a Boolean parameter called caseSensitive to determine whether the Mapper class should treat upper and lower case letters as different (case-sensitive) or whether all letters should be converted to lower case (case-insensitive).
Write down the Mapper output, Reducer input, and Reducer output using the case- insensitive version of your program for the test input provided above.

 import java.util.HashMap;
import java.util.Set;
class Untitled {
    public static double foo(String s, Boolean caseSensitive)
    {
        HashMap map = new HashMap();
        String[] words = s.split("[\\,\\(\\)\\.\\s\\r\\n\\-]");
        for (String item : words)
        {
            if (item.trim().equals("")) continue;
            if (!caseSensitive) item = item.toLowerCase();
            if (!map.containsKey(item)) map.put(item, item.length());
        }
        double r = 0.0;
        Set<String> wl = map.keySet();
        for (String w : wl) r += (double)w.length();
        r /= (double)wl.size();
        return r;
    }

    public static void main(String[] args) {
        String s = "You will write an Average Word Length program that uses a Boolean parameter called caseSensitive to determine whether the Mapper class should treat upper and lower case letters as different (case-sensitive) or whether all letters should be converted to lower case (case-insensitive).\r\nWrite down the Mapper output, Reducer input, and Reducer output using the case- insensitive version of your program for the test input provided above.";     
        System.out.println(foo(s, true));
        System.out.println(foo(s, false));
    }
}

根据你的题目，你求的是单词的平均长度，首先需要分离出句子中有多少单词，并且装入map，然后还需要判断大小写。你确认你理解了题目么？

运行结果：
5.326530612244898
5.333333333333333