无效的键码@java

I'm working on a system to type things automatically with java. This is how I write it:

public void typeMessage(String message) {
    for (char c : message.toCharArray()) {
        int code = c;
        if (code > 96 && code < 123) 
            code = code - 32;
        if (c == '@') {
            robot.keyPress(VK_SHIFT);
            robot.keyPress(VK_AT);
            robot.keyRelease(VK_SHIFT);
            robot.keyRelease(VK_AT);
        } else {
            type(code);
        }
    }
    type(VK_ENTER);
}

但是我收到了这个错误:

    Exception in thread "Thread-2" java.lang.IllegalArgumentException: Invalid key code

    robot.keyPress(VK_AT);