title: Is it a bad practice to have multiple classes in the same file?
body: <p>I used to have one class for one file. For example <em>car.cs</em> has the class <em>car</em>. But as I program more classes, I would like to add them to the same file. For example <em>car.cs</em> has the class <em>car</em> and the <em>door</em> class, etc.</p>
  
  <p>My question is good for Java, C#, PHP or any other programming language. Should I try not having multiple classes in the same file or is it ok?</p>