Design and Architectural Principles - Java 8 Lambdas - page 129

inheritance to build up our algorithm. Let's look at how we would implement our LoanAp-
plication algorithm this way, in Example 8-23 !

Example 8-23. The special case of an employee applying for a loan
public public class class LoanApplication LoanApplication {

private private final final Criteria identity ;

private private final final Criteria creditHistory ;

private private final final Criteria incomeHistory ;

public public LoanApplication ( Criteria identity ,

Criteria creditHistory ,
Criteria incomeHistory ) {

this this . identity = identity ;

this this . creditHistory = creditHistory ;

this this . incomeHistory = incomeHistory ;

}

public public void void checkLoanApplication () throws throws ApplicationDenied {

identity . check ();
creditHistory . check ();
incomeHistory . check ();
reportFindings ();

}

private private void void reportFindings () {

As you can see, instead of having a series of abstract methods we've got fields called iden-
tity , creditHistory , and incomeHistory . Each of these fields implements our Criteria
functional interface. The Criteria interface checks a criterion and throws a domain excep-
tion if there's an error in passing the criterion. We could have chosen to return a domain class
from the check method in order to denote failure or success, but continuing with an excep-
tion follows the broader pattern set out in the original implementation (see Example 8-24 ) .

Example 8-24. A Criteria functional interface that throws an exception if our application
fails
public

public interface interface Criteria Criteria {

public public void void check () throws throws ApplicationDenied ;

}