题目：
  每个句子有多个单词组成，句子中的每个单词的长度都可能不一样，我们假设每个单词的长度Ni为该单词的重量，你需要做的就是给出整个句子的平均重量。

保留两位小数的输出方法：

System.out.printf("%.2f",变量名);

// We have imported the necessary tool classes.
// If you need to import additional packages or classes, please import here.public class Main {public static void main(String[] args) {// please define the JAVA input here. For example: Scanner s = new Scanner(System.in);// please finish the function body here.// please define the JAVA output here. For example: System.out.println(s.nextInt());Scanner sc = new Scanner(System.in);String s = sc.nextLine();float wordsWeight = 0;float wordsNumber = 1;for(int i = 0; i < s.length(); i++){if(s.charAt(i) == ' ') wordsNumber++;else wordsWeight++;}float res = wordsWeight / wordsNumber;System.out.printf("%.2f",res);}
}