src/main/java/com/bazaarvoice/jackson/rison/IdentifierUtils.java
public static boolean isIdStrict(String string) {
        int len = string.length();
        if (len == 0) {
            return false;
        }
        if (!isIdStartStrict(string.charAt(0))) {
            return false;
        }
        for (int i = 1; i < len; i++) {
            if (!isIdCharStrict(string.charAt(i))) {
                return false;
            }
        }
        return true;
    }
public static boolean isIdStrict(String string) {
        int len = string.length();
        if (len == 0) {
            return false;
        }
        if (!isIdStartStrict(string.charAt(0))) {
            return false;
        }
        for (int i = 1; i < len; i++) {
            if (!isIdCharStrict(string.charAt(i))) {
                return false;
            }
        }
        return true;
    }
Returns true if a string does not need to be quoted when serialized.
Uses the strict definition described in the Rison specification, appropriate for encoding.