├── src └── main │ └── java │ └── com │ └── google │ └── developers │ └── wallet │ ├── PassInformation.java │ ├── UserProfile.java │ ├── singleton │ ├── revisited │ │ └── RevisitedSingleton.java │ └── legacy │ │ └── LegacySingleton.java │ ├── specification │ ├── revisited │ │ └── RevisitedSpecification.java │ └── legacy │ │ └── LegacySpecification.java │ ├── visitor │ ├── revisited │ │ └── RevisitedVisitor.java │ └── legacy │ │ └── LegacyVisitor.java │ ├── template │ ├── revisited │ │ └── RevisitedTemplateMethod.java │ └── legacy │ │ └── LegacyTemplateMethod.java │ ├── strategy │ ├── revisited │ │ └── RevisitedStrategy.java │ └── legacy │ │ └── LegacyStrategy.java │ ├── interpreter │ ├── revisited │ │ └── RevisitedInterpreter.java │ └── legacy │ │ └── LegacyInterpreter.java │ └── chain │ ├── revisited │ └── RevisitedChainOfResponsibility.java │ └── legacy │ └── LegacyChainOfResponsibility.java ├── README.md ├── .gitignore ├── pom.xml └── LICENSE /src/main/java/com/google/developers/wallet/PassInformation.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet; 2 | 3 | public record PassInformation(UserProfile userProfile) { 4 | } 5 | -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/UserProfile.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet; 2 | 3 | public record UserProfile(boolean hasGoogleWalletPass, boolean allowsEmail, boolean allowsSms) { 4 | 5 | } 6 | -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/singleton/revisited/RevisitedSingleton.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.singleton.revisited; 2 | 3 | public enum RevisitedSingleton { 4 | INSTANCE; 5 | } 6 | -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/singleton/legacy/LegacySingleton.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.singleton.legacy; 2 | 3 | public class LegacySingleton { 4 | 5 | private static final LegacySingleton INSTANCE = new LegacySingleton(); 6 | 7 | public static LegacySingleton getInstance() { 8 | return INSTANCE; 9 | } 10 | 11 | } 12 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Revisiting Design Patterns After 20 2 | 3 | The title is a bad pun about the 20+ years since the original Design Patterns book release and the Java 20 release on March 21, 2023. 4 | 5 | We're revisiting some popular Design Patterns using Java 20+ features. 6 | 7 | These are the ones we're covering so far: 8 | - Strategy 9 | - Template Method 10 | - Singleton 11 | - Interpreter 12 | - Chain of Responsibility 13 | - Visitor 14 | - Specification -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/specification/revisited/RevisitedSpecification.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.specification.revisited; 2 | 3 | import java.util.function.Predicate; 4 | 5 | public class RevisitedSpecification { 6 | 7 | public static void main(String[] args) { 8 | Predicate rightLength = s -> s.length() == 16; 9 | Predicate isNumeric = s -> s.matches("\\d+"); 10 | 11 | Predicate potentialCreditCardNumber = rightLength.and(isNumeric); 12 | System.out.println(potentialCreditCardNumber.test("1234123412341234")); 13 | } 14 | 15 | } 16 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | target/ 2 | !.mvn/wrapper/maven-wrapper.jar 3 | !**/src/main/**/target/ 4 | !**/src/test/**/target/ 5 | 6 | ### IntelliJ IDEA ### 7 | .idea 8 | .idea/modules.xml 9 | .idea/jarRepositories.xml 10 | .idea/compiler.xml 11 | .idea/libraries/ 12 | *.iws 13 | *.iml 14 | *.ipr 15 | 16 | ### Eclipse ### 17 | .apt_generated 18 | .classpath 19 | .factorypath 20 | .project 21 | .settings 22 | .springBeans 23 | .sts4-cache 24 | 25 | ### NetBeans ### 26 | /nbproject/private/ 27 | /nbbuild/ 28 | /dist/ 29 | /nbdist/ 30 | /.nb-gradle/ 31 | build/ 32 | !**/src/main/**/build/ 33 | !**/src/test/**/build/ 34 | 35 | ### VS Code ### 36 | .vscode/ 37 | 38 | ### Mac OS ### 39 | .DS_Store 40 | -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/visitor/revisited/RevisitedVisitor.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.visitor.revisited; 2 | 3 | public class RevisitedVisitor { 4 | 5 | public static void main(String[] args) { 6 | GoogleWalletPass pass = new Loyalty(); 7 | 8 | } 9 | 10 | int doSomething(GoogleWalletPass pass) { 11 | return switch (pass) { 12 | case Loyalty l when l.size > 10 -> 1; 13 | case Loyalty l -> 3; 14 | case EventTicket e -> 2; 15 | }; 16 | } 17 | 18 | } 19 | 20 | abstract sealed class GoogleWalletPass permits Loyalty, EventTicket{ 21 | 22 | } 23 | 24 | final class Loyalty extends GoogleWalletPass { 25 | 26 | public int size; 27 | } 28 | 29 | final class EventTicket extends GoogleWalletPass{} -------------------------------------------------------------------------------- /pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | com.google.developers.wallet 8 | revisiting-design-patterns 9 | 1.0-SNAPSHOT 10 | 11 | 12 | 13 | org.apache.maven.plugins 14 | maven-compiler-plugin 15 | 16 | 20 17 | 20 18 | --enable-preview 19 | 20 | 21 | 22 | 23 | 24 | 25 | 20 26 | 20 27 | UTF-8 28 | 29 | 30 | -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/visitor/legacy/LegacyVisitor.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.visitor.legacy; 2 | 3 | public class LegacyVisitor { 4 | 5 | public static void main(String[] args) { 6 | GoogleWalletPass card = new LoyaltyCard(); 7 | card.accept(new Visitor() { 8 | @Override 9 | public Object visit(LoyaltyCard loyaltyCard) { 10 | return null; 11 | } 12 | 13 | @Override 14 | public Object visit(EventTicket eventTicket) { 15 | return null; 16 | } 17 | }); 18 | } 19 | 20 | } 21 | 22 | interface Visitor { 23 | T visit(LoyaltyCard loyaltyCard); 24 | 25 | T visit(EventTicket eventTicket); 26 | 27 | } 28 | 29 | abstract class GoogleWalletPass { 30 | 31 | public abstract T accept(Visitor visitor); 32 | 33 | } 34 | 35 | class LoyaltyCard extends GoogleWalletPass { 36 | 37 | @Override 38 | public T accept(Visitor visitor) { 39 | return visitor.visit(this); 40 | } 41 | } 42 | 43 | class EventTicket extends GoogleWalletPass { 44 | 45 | @Override 46 | public T accept(Visitor visitor) { 47 | return visitor.visit(this); 48 | } 49 | } -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/template/revisited/RevisitedTemplateMethod.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.template.revisited; 2 | 3 | import com.google.developers.wallet.PassInformation; 4 | import com.google.developers.wallet.UserProfile; 5 | 6 | import java.util.Map; 7 | import java.util.function.Function; 8 | 9 | public class RevisitedTemplateMethod { 10 | 11 | public static void main(String[] args) { 12 | var passInformation = new PassInformation(new UserProfile(true, true, true)); 13 | getGoogleWalletPassCreator().createPass(passInformation); 14 | } 15 | 16 | public static GoogleWalletPassCreator getGoogleWalletPassCreator() { 17 | return new GoogleWalletPassCreator(p -> Map.of("eventTicket", "I'm going!")); 18 | } 19 | } 20 | 21 | class GoogleWalletPassCreator { 22 | 23 | private final Function> strategy; 24 | 25 | public GoogleWalletPassCreator(Function> strategy) { 26 | this.strategy = strategy; 27 | } 28 | 29 | protected void authenticate() { 30 | System.out.println("Authenticating..."); 31 | } 32 | 33 | public void createPass(PassInformation passInformation) { 34 | authenticate(); 35 | Map map = strategy.apply(passInformation); 36 | System.out.println(signToken(map)); 37 | } 38 | 39 | protected String signToken(Map properties) { 40 | return properties.values().stream().findFirst().get(); 41 | } 42 | } -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/strategy/revisited/RevisitedStrategy.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.strategy.revisited; 2 | 3 | import com.google.developers.wallet.PassInformation; 4 | import com.google.developers.wallet.UserProfile; 5 | 6 | import java.util.function.Function; 7 | 8 | public class RevisitedStrategy { 9 | 10 | public static void main(String[] args) { 11 | var endpoint = getEndpoint(); 12 | var passInformation = new PassInformation(new UserProfile(true, true, true)); 13 | String jwt = endpoint.get(passInformation); 14 | System.out.println(jwt); 15 | } 16 | 17 | public static GoogleWalletEndpoint getEndpoint() { 18 | var endpoint = new GoogleWalletEndpoint(); 19 | endpoint.setStrategy(pass -> "abc"); 20 | endpoint.setStrategy(new AddToGoogleWalletLink()::complete); 21 | endpoint.setStrategy(new AddToGoogleWalletLink()::preCreated); 22 | return endpoint; 23 | } 24 | 25 | } 26 | 27 | class GoogleWalletEndpoint { 28 | 29 | private Function strategy; 30 | 31 | public String get(PassInformation passInformation) { 32 | return strategy.apply(passInformation); 33 | } 34 | 35 | public void setStrategy(Function strategy) { 36 | this.strategy = strategy; 37 | } 38 | 39 | } 40 | 41 | class AddToGoogleWalletLink { 42 | 43 | public String complete(PassInformation information) { 44 | return "JWT with complete information."; 45 | } 46 | 47 | public String preCreated(PassInformation information) { 48 | return "JWT with just the IDs of the objects."; 49 | } 50 | } 51 | -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/specification/legacy/LegacySpecification.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.specification.legacy; 2 | 3 | public class LegacySpecification { 4 | 5 | public static void main(String[] args) { 6 | Specification rightLength = s -> s.length() == 16; 7 | Specification isNumeric = s -> s.matches("\\d+"); 8 | 9 | Specification potentialCreditCardNumber = rightLength.and(isNumeric); 10 | System.out.println(potentialCreditCardNumber.isSatisfiedBy("1234123412341234")); 11 | } 12 | 13 | } 14 | 15 | interface Specification { 16 | boolean isSatisfiedBy(String s); 17 | 18 | default Specification and(Specification other) { 19 | return new AndSpecification(this, other); 20 | } 21 | default Specification or(Specification other) { 22 | return new OrSpecification(this, other); 23 | } 24 | default Specification not(Specification other) { 25 | return new NotSpecification(other); 26 | } 27 | 28 | } 29 | 30 | record AndSpecification(Specification left, Specification right) implements Specification { 31 | 32 | @Override 33 | public boolean isSatisfiedBy(String s) { 34 | return left.isSatisfiedBy(s) && right.isSatisfiedBy(s); 35 | } 36 | 37 | } 38 | 39 | record OrSpecification(Specification left, Specification right) implements Specification { 40 | 41 | @Override 42 | public boolean isSatisfiedBy(String s) { 43 | return left.isSatisfiedBy(s) || right.isSatisfiedBy(s); 44 | } 45 | 46 | } 47 | 48 | record NotSpecification(Specification specification) implements Specification { 49 | 50 | @Override 51 | public boolean isSatisfiedBy(String s) { 52 | return !specification.isSatisfiedBy(s); 53 | } 54 | 55 | } 56 | 57 | -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/interpreter/revisited/RevisitedInterpreter.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.interpreter.revisited; 2 | 3 | import java.util.Arrays; 4 | import java.util.Map; 5 | import java.util.Optional; 6 | import java.util.Stack; 7 | import java.util.function.IntBinaryOperator; 8 | import java.util.stream.Collectors; 9 | 10 | public class RevisitedInterpreter { 11 | 12 | public static void main(String[] args) { 13 | System.out.println(evaluate("5 7 + 10 5 - -")); 14 | } 15 | 16 | public static int evaluate(String expression) { 17 | Stack stack = new Stack<>(); 18 | for (String s : expression.split(" ")) { 19 | Operation.fromString(s) 20 | .ifPresentOrElse( 21 | o -> stack.push(o.apply(stack.pop(), stack.pop())), 22 | () -> stack.push(Integer.parseInt(s)) 23 | ); 24 | } 25 | return stack.pop(); 26 | } 27 | } 28 | 29 | enum Operation { 30 | ADD("+", (x, y) -> y + x), 31 | SUBTRACT("-", (x, y) -> y - x); 32 | 33 | public static final Map valueMap = 34 | Arrays.stream(values()).collect(Collectors.toUnmodifiableMap(o -> o.stringValue, o -> o)); 35 | 36 | private final String stringValue; 37 | 38 | private final IntBinaryOperator operator; 39 | 40 | Operation(String stringValue, IntBinaryOperator operator) { 41 | this.stringValue = stringValue; 42 | this.operator = operator; 43 | } 44 | 45 | public static Optional fromString(String s) { 46 | return Optional.ofNullable(valueMap.get(s)); 47 | } 48 | 49 | public int apply(int x, int y) { 50 | return operator.applyAsInt(x, y); 51 | } 52 | } -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/strategy/legacy/LegacyStrategy.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.strategy.legacy; 2 | 3 | import com.google.developers.wallet.PassInformation; 4 | import com.google.developers.wallet.UserProfile; 5 | 6 | public class LegacyStrategy { 7 | 8 | public static void main(String[] args) { 9 | var endpoint = getEndpoint(); 10 | var passInformation = new PassInformation(new UserProfile(true, true, true)); 11 | String jwt = endpoint.get(passInformation); 12 | System.out.println(jwt); 13 | } 14 | 15 | public static GoogleWalletEndpoint getEndpoint() { 16 | var endpoint = new GoogleWalletEndpoint(); 17 | endpoint.setStrategy(new CompleteJwtAddToGoogleWalletStrategy()); 18 | return endpoint; 19 | } 20 | 21 | } 22 | 23 | class GoogleWalletEndpoint { 24 | 25 | private AddToGoogleWalletStrategy strategy; 26 | 27 | public String get(PassInformation passInformation) { 28 | return strategy.createLink(passInformation); 29 | } 30 | 31 | public void setStrategy(AddToGoogleWalletStrategy strategy) { 32 | this.strategy = strategy; 33 | } 34 | } 35 | 36 | interface AddToGoogleWalletStrategy { 37 | 38 | String createLink(PassInformation information); 39 | 40 | } 41 | 42 | class CompleteJwtAddToGoogleWalletStrategy implements AddToGoogleWalletStrategy { 43 | 44 | @Override 45 | public String createLink(PassInformation information) { 46 | return "JWT with complete information."; 47 | } 48 | } 49 | 50 | class PreCreatedJwtAddToGoogleWalletStrategy implements AddToGoogleWalletStrategy { 51 | 52 | @Override 53 | public String createLink(PassInformation information) { 54 | return "JWT with just the IDs of the objects."; 55 | } 56 | 57 | } -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/interpreter/legacy/LegacyInterpreter.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.interpreter.legacy; 2 | 3 | import java.util.Arrays; 4 | import java.util.Map; 5 | import java.util.Optional; 6 | import java.util.Stack; 7 | import java.util.stream.Collectors; 8 | 9 | public class LegacyInterpreter { 10 | 11 | public static void main(String[] args) { 12 | System.out.println(evaluate("5 7 + 10 5 - -")); 13 | } 14 | 15 | public static int evaluate(String expression) { 16 | Stack stack = new Stack<>(); 17 | for (String s : expression.split(" ")) { 18 | Operation operation = Operation.fromString(s); 19 | if (operation != null) { 20 | Integer right = stack.pop(); 21 | Integer left = stack.pop(); 22 | stack.push(operation.apply(left, right)); 23 | } else { 24 | stack.push(Integer.parseInt(s)); 25 | } 26 | } 27 | return stack.pop(); 28 | } 29 | } 30 | 31 | enum Operation { 32 | ADD("+") { 33 | @Override 34 | public int apply(int x, int y) { 35 | return x + y; 36 | } 37 | }, 38 | SUBTRACT("-") { 39 | @Override 40 | public int apply(int x, int y) { 41 | return x - y; 42 | } 43 | }; 44 | 45 | public static final Map valueMap = 46 | Arrays.stream(values()).collect(Collectors.toUnmodifiableMap(o -> o.stringValue, o -> o)); 47 | 48 | private final String stringValue; 49 | 50 | Operation(String stringValue) { 51 | this.stringValue = stringValue; 52 | } 53 | 54 | public static Operation fromString(String s) { 55 | return valueMap.get(s); 56 | } 57 | 58 | public abstract int apply(int x, int y); 59 | 60 | } -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/template/legacy/LegacyTemplateMethod.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.template.legacy; 2 | 3 | import com.google.developers.wallet.PassInformation; 4 | import com.google.developers.wallet.UserProfile; 5 | 6 | import java.util.HashMap; 7 | import java.util.Map; 8 | 9 | public class LegacyTemplateMethod { 10 | 11 | public static void main(String[] args) { 12 | var passInformation = new PassInformation(new UserProfile(true, true, true)); 13 | getGoogleWalletPassCreator().createPass(passInformation); 14 | } 15 | 16 | public static GoogleWalletPassCreator getGoogleWalletPassCreator() { 17 | return new EventTicketGoogleWalletPassCreator(); 18 | } 19 | } 20 | 21 | abstract class GoogleWalletPassCreator { 22 | 23 | protected void authenticate() { 24 | System.out.println("Authenticating..."); 25 | } 26 | 27 | public void createPass(PassInformation passInformation) { 28 | authenticate(); 29 | Map map = doCreatePass(passInformation); 30 | System.out.println(signToken(map)); 31 | } 32 | 33 | protected abstract Map doCreatePass(PassInformation passInformation); 34 | 35 | protected String signToken(Map properties) { 36 | return properties.values().stream().findFirst().get(); 37 | } 38 | } 39 | 40 | class LoyaltyGoogleWalletPassCreator extends GoogleWalletPassCreator { 41 | 42 | @Override 43 | protected Map doCreatePass(PassInformation passInformation) { 44 | return Map.of("loyalty", "I'm loyal"); 45 | } 46 | 47 | } 48 | 49 | class EventTicketGoogleWalletPassCreator extends GoogleWalletPassCreator { 50 | @Override 51 | protected Map doCreatePass(PassInformation passInformation) { 52 | return Map.of("eventTicket", "I'm going!"); 53 | } 54 | 55 | } -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/chain/revisited/RevisitedChainOfResponsibility.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.chain.revisited; 2 | 3 | import com.google.developers.wallet.UserProfile; 4 | 5 | import java.util.function.Consumer; 6 | import java.util.function.Predicate; 7 | import java.util.stream.Stream; 8 | 9 | public class RevisitedChainOfResponsibility { 10 | 11 | public static void main(String[] args) { 12 | var userProfile = new UserProfile(false, true, false); 13 | Stream.of( 14 | new GoogleWalletPassUpdateNotifier(), 15 | new SmsNotifier(), 16 | new EmailNotifier() 17 | ) 18 | .filter(n -> n.test(userProfile)) 19 | .findFirst() 20 | .ifPresent(n -> n.accept(userProfile)); 21 | 22 | Stream.of(new UserNotifier(UserProfile::allowsSms, u -> System.out.println("SMS sent"))) 23 | .filter(u -> u.predicate().test(userProfile)) 24 | .findFirst() 25 | .ifPresent(u -> u.consumer().accept(userProfile)); 26 | } 27 | 28 | } 29 | 30 | record UserNotifier(Predicate predicate, Consumer consumer) { 31 | 32 | } 33 | 34 | class GoogleWalletPassUpdateNotifier implements Consumer, Predicate { 35 | @Override 36 | public void accept(UserProfile profile) { 37 | System.out.println("Google Wallet Pass updated."); 38 | } 39 | 40 | @Override 41 | public boolean test(UserProfile profile) { 42 | return profile.hasGoogleWalletPass(); 43 | } 44 | } 45 | 46 | class EmailNotifier implements Consumer, Predicate { 47 | @Override 48 | public void accept(UserProfile profile) { 49 | System.out.println("Email sent."); 50 | } 51 | 52 | @Override 53 | public boolean test(UserProfile profile) { 54 | return profile.allowsEmail(); 55 | } 56 | } 57 | 58 | class SmsNotifier implements Consumer, Predicate { 59 | @Override 60 | public void accept(UserProfile profile) { 61 | System.out.println("SMS sent."); 62 | } 63 | 64 | @Override 65 | public boolean test(UserProfile userProfile) { 66 | return userProfile.allowsSms(); 67 | } 68 | } -------------------------------------------------------------------------------- /src/main/java/com/google/developers/wallet/chain/legacy/LegacyChainOfResponsibility.java: -------------------------------------------------------------------------------- 1 | package com.google.developers.wallet.chain.legacy; 2 | 3 | import com.google.developers.wallet.UserProfile; 4 | 5 | public class LegacyChainOfResponsibility { 6 | 7 | public static void main(String[] args) { 8 | var userProfile = new UserProfile(false, true, false); 9 | var userNotifier = createNotifier(); 10 | userNotifier.notify(userProfile); 11 | } 12 | 13 | public static UserNotifier createNotifier() { 14 | var googleWalletPassUpdateNotifier = new GoogleWalletPassUpdateNotifier(); 15 | var emailNotifier = new EmailNotifier(); 16 | var smsNotifier = new SmsNotifier(); 17 | 18 | googleWalletPassUpdateNotifier.setNextNotifier(emailNotifier); 19 | emailNotifier.setNextNotifier(smsNotifier); 20 | 21 | return googleWalletPassUpdateNotifier; 22 | } 23 | } 24 | 25 | interface UserNotifier { 26 | 27 | void notify(UserProfile profile); 28 | 29 | void setNextNotifier(UserNotifier notifier); 30 | 31 | } 32 | 33 | abstract class AbstractUserNotifier implements UserNotifier { 34 | 35 | protected UserNotifier nextNotifier; 36 | 37 | @Override 38 | public void setNextNotifier(UserNotifier notifier) { 39 | this.nextNotifier = notifier; 40 | } 41 | } 42 | 43 | class GoogleWalletPassUpdateNotifier extends AbstractUserNotifier { 44 | @Override 45 | public void notify(UserProfile profile) { 46 | if (profile.hasGoogleWalletPass()) { 47 | System.out.println("Google Wallet Pass updated."); 48 | } else if (nextNotifier != null) { 49 | nextNotifier.notify(profile); 50 | } else { 51 | throw new RuntimeException("No notification sent"); 52 | } 53 | } 54 | } 55 | 56 | class EmailNotifier extends AbstractUserNotifier { 57 | @Override 58 | public void notify(UserProfile profile) { 59 | if (profile.allowsEmail()) { 60 | System.out.println("Email sent"); 61 | } else if (nextNotifier != null) { 62 | nextNotifier.notify(profile); 63 | } else { 64 | throw new RuntimeException("No notification sent"); 65 | } 66 | } 67 | } 68 | 69 | class SmsNotifier extends AbstractUserNotifier { 70 | @Override 71 | public void notify(UserProfile profile) { 72 | if (profile.allowsSms()) { 73 | System.out.println("SMS sent"); 74 | } else if (nextNotifier != null) { 75 | nextNotifier.notify(profile); 76 | } else { 77 | throw new RuntimeException("No notification sent"); 78 | } 79 | } 80 | } -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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