More Features of the Java Language

Using an Interface as a Type

When you define a new interface, you are in essence defining a new reference data type. You can use interface names anywhere you can use any other data type name.

For example, the AlarmClock class uses the Sleeper type in two places:

• To declare an array of Sleepers (shown in bold):

  private Sleeper[] sleepers = new Sleeper[MAX_CAPACITY];
  

• As an argument to letMeSleepFor (shown in bold):

  private boolean letMeSleepFor(Sleeper theSleeper, int time)
  {
  . . .
  }
  

More Features of the Java Language