So even though we think of conditions as being Boolean values true or false, really underneath the hood true means anything other than zero.

即使我们考虑,布尔值的真假条件，在底层“真“表示非零。

哈佛公开课 - 计算机科学课程节选

If you want to make sure both conditions are true and they both have to be true for any code to be executed, use ampersand ampersand.

如果你想保证两个条件都成立,或者它们两个都必须为真值，才能执行一些代码，那就使用“&&“

哈佛公开课 - 计算机科学课程节选