1 String.valueOf: 可以把很多类型的数值或者字符数组转化为String
char c = 'a';
System.out.println(String.valueOf(c));
System.out.println(String.valueOf("abc".charAt(2)));
System.out.println(String.valueOf(65));
System.out.println(String.valueOf(65.365));
System.out.println(String.valueOf(new char[]{'d', 'c'}));
输出:
a
c
65
65.365
dc
2 "acasdc".toCharArray():把字符串转化为字符数组
3 char<->int互转,(int)'9'=57,(char)57='9'
4 int每个数字转化为字符,57->'5','7':String.va