BetterNamingAndSomeRefactoring.java

//
// CHALLENGE (work in pairs):
// Move from f(o) -> o.f() and make sure that the code is CQS compliant.
//


// 1 
// Turn on object-thinking and re-design the code accordingly
/*
class CsvParser<T extends Line> { 
    Collection<T> parse(File location) { 
    } 
} */

// answer 1
File file = new File("");
class CsvFile<T extends Line> {
    private final Path p;
    private Collection<T> lines;
    CsvFile(Path path) {
        this.p = path;
        // populate lines
    }
    Collection<T> lines() {
        return immutableList.of(lines);
    }
    Stream<T> lines() {
        return lines.stream();
    }
}
// answer 2
// with Guava
class Csv extends ForwardingCollection<T extends Line> {
    Collection<T> lines;
    Csv (Path path) {
        Files.readLines(path);
    }
    @Override
    protected Collection<T> delegate() {
        return immutableCopy.of(lines);
    }
}
new Csv<Line>(path).stream()...
// 2
// Turn on object-thinking and re-design the code accordingly
interface Pinger { 
    void sendPing(); 
}
(new Pinger()).sendPing();
//
class Channel {
    Channel(IP destination) {
    }
    void ping() {
    }
}
//
class Ping {
    void send();
}
class Host {
    void ping();
}

// 3
// rename the method to improve readability
/*interface Input {
  boolean validate();
}*/
interface Input {
  boolean isValid();
}
//if (Input().validate()) {}
if (Input().isValid()) {}

// 4 
// turn procedural code into object-oriented
class MortgageRiskService {  
  BigDecimal calculateRisk(MortageApplication mortgageApplication) {
    ...
  }
  boolean isTolerable(BigDecimal risk) {
    ...
  }
  boolean areRisksEquivalent(BigDecimal oneRisk, BigDecimal otherRisk) {
    ...
  }
}
MortgageRiskService(application).isTolerable();
//
class Mortgage {
    private final MortgageRisk mr;
    Mortgage(MorgageAppliaction ma) {
        //this.mr = new MortgageRisk(this);
    }
    MortageRisk risk() {
        return this.mr;
    }
}
class MortgageRisk as BigDecimal {
    MortgageRisk(Mortgage mortgage) {
        ...
    }
    boolean isTolerable() {...}
    boolean equals(MortgageRisk other) {...}
}
Mortgage.risk().isTolerable();
//correct one
class MortgageRisk {
    private final BigDecimal risk;
    MortgageRisk(MortgageApplication mortgageApplication) {
        // calc
        this.risk = ...;
    }
    boolean isTolerable() {...}
    boolean isEquivalentTo(MortgageRisk other) {...}
}
// 5
// Iovation - a company that maintains a blacklist of email addresses and corresponding IPs
interface IovationService { 
    boolean shouldBlockWebsiteVisitor(IovationClientRequest request); 
} 

interface IovationClientRequest { 
     String getEmail(); 
     String getIpAddress(); 
} 
//
class Blacklist {
    Collection<IovationClientRequest> clients;
    public void blockClient(IovationClientRequest client) {
        clients.push(client);
    }
    boolean contains(IovationClientRequest client) {
        clients.contains(client);
    }
}

BlackList bl;
bl.blockClient(...);
bl.contains(client);
// correct
interface BlackList {
    boolean contains(websiteVisitor);
    void put(websiteVisitor);
}
// 6
interface AnonymousUserAuthenticator {
    Token authenticate(String username, String password) throws WrongAuthenticationCredentialsProvided;
}
//----
Class WrongAuthenticationCredentialsProvidedException extends RuntimeException;
Class UserIsNotAuthenticatedException extends RuntimeException;
interface Creds {
    String username();
    String password();
}
class User {
    private final Creds c;
    private Token t;
    User(Creds c) {
        this.c = c;
        this.t = ;// try auth
        if (/*auth failed*/) {
            throw new WrongAuthenticationCredentialsProvidedException("Some meaningful text");
        }
    }
    Token token() {
        if (token == null) {
            throw new UserIsNotAuthenticatedException("Some meaningful text");
        }
        return this.t;
    }
}
Token t = (new User(new Creds("username", "password"))).token();
// correct
class Authorization {
    Authorization(Credentials credentials) {
    }
    Token token() { // for exceptions - test cases
    }
}
// 7
interface Suite { 
    interface SuiteTest { 
        void print();
        boolean successful();
    }
    void runAndWait();
    Collection<SuiteTest> listSuiteTests(); 
} 

suite.runAndWait()
for (SuiteTest suiteTest : suite.listSuiteTests()) { 
    if (!suiteTest.successful() ) {
        // pretty printing 
        suiteTest.print();            
    }
}
//

interface Suite { 
    interface Test { 
        void prettyPrint();
        boolean isSuccessful();
    }
    void execTests();
    Collection<Test> tests(); 
    //Collection<Test> printFailed() {
    //    for (Test t : this.tests()) {
    //        if (!t.passed()) {
    //            t.prettyPrint();
    //        }
    //    }
    //}
} 
suite.execTests()
//suite.printFailed()
suite
    .tests()
    .filter(Predicate.not(Test::isSuccessful))
    .forEach(Test::prettyPrint)
// 8.1
// What's the expected return type of the method (if you look at the code from the outside?)
// If you didn't expect boolean (as most develoeprs), rename it so it's clear that the boolean is returned
enum Severity {
  boolean isMajor();
}

// 8.2
// What's the expected return type of the method (if you look at the code from the outside?)
// If you didn't expect boolean (as most develoeprs), rename it so it's clear that the boolean is returned
class Specification {
  boolean isSatisfiedBy(Entity entity);
}


// 9 SLAP!
boolean destroyButtonAvailable = 
    widgets
        .stream()
        .filter(Widget::isButton)
        .filter(button -> button.label().equals("Destroy The World"))
        .isPresent();

boolean destroyButtonAvailable = 
    widgets
        .stream()
        .filter(Widget::isButton)
        .map(Widget::label)
        .any("Destroy The World"::equals);

// 10 transform a full name into a twitter handle. Jack Ma must become @jack.ma
String fullName = "Jack Ma";
...
Class Name as String {
    String handle() {
        return "@".concat(fullName.toLowerCase().replace(" ", "."));
    }
}
String twitterHandle = Name(fullName).handle();
// hmm...
String twitterHandle = Stream
    .of("Jack Ma")
    .map(it -> it.toLowerCase())
    .map(it -> it.replace(" ", "."))
    .map(it -> "@".concat(it))
    .findFirst()
    .get();