从Java字符串中以长度1的字符串返回的第一个字母的最佳方法是什么？

substring(0, 1)

    String example = "something";    String firstLetter  = "";    long l=System.nanoTime();    firstLetter = String.valueOf(example.charAt(0));    System.out.println("String.valueOf: "+ (System.nanoTime()-l));    l=System.nanoTime();    firstLetter = Character.toString(example.charAt(0));    System.out.println("Character.toString: "+ (System.nanoTime()-l));    l=System.nanoTime();    firstLetter = example.substring(0, 1);    System.out.println("substring: "+ (System.nanoTime()-l));

输出：

String.valueOf: 38553Character.toString: 30451substring: 8660