Any system property set with `-Dkey=value` can be retrieved as a String using `System.getProperty("key")`. But you can also get certain system properties casted to a specific type, e.g.:

```
Boolean.getBoolean("key"); //Returns true if value==true
Integer.getInteger("key"); //Returns value if exists & is number, else null
Long.getLong("key"); //Ditto as for Integer

```

Are there any other classes with a `static getSomeClass(String systemPropertyKey)` method? Why don't `Byte`, `Float`, or `Double` have them, but the other primitive wrappers do (or what *might* be the reason)?