Explicit delegation can be implemented by passing the delegate object to the delegating object. We can do this in any object-oriented language, such as Java. Let's create a Calculator interface:
public interface Calculator { int performOperation(String operand);}
We'll also create a CalculatorBrain class that implements the Calculator interface:
public class CalculatorBrain implements Calculator { public int performOperation(String operand) { throw new IllegalStateException("Not implemented!"); }}
Now we'll implement a CalculatorMachine class. An instance of this class is a delegating object that delegates authority to an instance of Calculator, which is a delegate object. Let's create the CalculatorMachine class, which ...
