写一个函数，求一个字符串的长度，在 main 函数中输入字符串，并输出其长度

package cskaoyan;
 
public class cskaoyan38 {
 
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        java.util.Scanner in = new java.util.Scanner(System.in);
        System.out.println("please input a string:");
        String str = in.nextLine();
        char[] arr = str.toCharArray();
        System.out.println("the string has " + arr.length + " characters.");
        in.close();
    }
}