Java Data Type - 如何大写字符串

public class Main {

  public static void main(String[] args) {
    String s = "this is a test";

    System.out.println(capitalize(s));
  }

  public static String capitalize(String s) {
    if (s.length() == 0) {
      return s;
    }

    return s.substring(0, 1).toUpperCase() + s.substring(1).toLowerCase();
  }
}