替换不在范围内的所有字符（Java String）
问题描述：
如何替换字符串中不符合条件的所有字符。我在使用NOT运算符时遇到了麻烦。
How do you replace all of the characters in a string that do not fit a criteria. I'm having trouble specifically with the NOT operator.
具体来说，我正在尝试删除所有不是数字的字符，到目前为止我已尝试过：
Specifically, I'm trying to remove all characters that are not a digit, I've tried this so far:
String number = "703-463-9281";
String number2 = number.replaceAll("[0-9]!", ""); // produces: "703-463-9281" (no change)
String number3 = number.replaceAll("[0-9]", ""); // produces: "--"
String number4 = number.replaceAll("![0-9]", ""); // produces: "703-463-9281" (no change)
String number6 = number.replaceAll("^[0-9]", ""); // produces: "03-463-9281"
答
解释一下：字符类开头的^将否定该类但它必须在类中才能工作。相反，字符类之外的字符是字符串/行开头的锚点。
To explain: The ^ at the start of a character class will negate that class But it has to be inside the class for that to work. The same character outside a character class is the anchor for start of string/line instead.
您可以尝试这样做：
"[^0-9]"