public String scanTypeName(SymbolTable symbolTable) {
        if (text.startsWith("\"@type\":\"", bp)) {
            int p = text.indexOf('"', bp + 9);
            if (p != -1) {
                bp += 9;
                int h = 0;
                for (int i = bp; i < p; i++) {
                    h = 31 * h + text.charAt(i);
                }
                String typeName = addSymbol(bp, p - bp, h, symbolTable);
                char separator = text.charAt(p + 1);
                if (separator != ',' && separator != ']') {
                    return null;
                }
                bp = p + 2;
                ch = text.charAt(bp);
                return typeName;
            }
        }

        return null;
    }
The value of a literal token, recorded as a string. For integers, leading 0x and 'l' suffixes are suppressed.
src/main/java/com/alibaba/fastjson/parser/JSONScanner.java