ToastUtils - helper class for Android SDK Toast
IMO this class isn't very useful (at least in a current shape).  


  In Toast class I often miss the call to show()


Well, it's not a bug, it's a feature. There are many situations when you only want to prepare your Toast using makeText() and show it later with show().  Moreover, you don't fix this "bug" with your class - there is still a makeText() method which does exactly what Toast used to do. And you still can forget to call show(). 


  Parameter length has type int. So a compiler couldn't detect invalid argument value


I wouldn't say that this is a bug, too. And you're fixing it in a bad way, again: 

   public static ToastUtils LONG = new ToastUtils(Toast.LENGTH_LONG);
   public static ToastUtils SHORT = new ToastUtils(Toast.LENGTH_SHORT);


So there can only be single instances of LONG and SHORT at the time. This will make many things complicated. 



To sum up, this is usage example of your class:

ToastUtils.LONG.show(context, R.string.greeting);

And this is the same without using your class:

Toast.makeText(context, R.string.greeting, Toast.LENGTH_LONG).show();

It's not a big improvement, is it?