在Java中检查两个参数，要么都不为空，要么都为空

Question

sendmail -from [e-mail] -password  foobar -subject "hello world"  -to [e-mail]

我如何优雅地检查这个？

现在我的方式是

if ((from != null && password == null) || (from == null && password != null)) {
    throw new RuntimeException("from and password either both exist or both not exist");
}

Answer 1

有一种使用^(XOR)运算符的方法：

if (from == null ^ password == null) {
    // Use RuntimeException if you need to
    throw new IllegalArgumentException("message");
}

如果只有一个变量为null，if条件将为true。

但我认为通常使用两个if条件和不同的异常消息会更好。你不能用一个条件来定义哪里出了问题。

if ((from == null) && (password != null)) {
    throw new IllegalArgumentException("If from is null, password must be null");
}
if ((from != null) && (password == null)) {
    throw new IllegalArgumentException("If from is not null, password must not be null");
}