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aplotnikovaplotnikov
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Add code examples
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‎src/main/java/io/github/aplotnikov/java_8_misuses/domain/Application.java‎

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package io.github.aplotnikov.java_8_misuses.domain;
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import lombok.Value;
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import java.math.BigDecimal;
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@Value
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public class Application {
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long id;
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BigDecimal amount;
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/domain/Client.java‎

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package io.github.aplotnikov.java_8_misuses.domain;
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import lombok.Value;
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import java.util.Optional;
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@Value
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public class Client {
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long id;
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public Loan getLastLoan() {
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return null;
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}
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public Optional<Loan> findLastLoan() {
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return Optional.empty();
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}
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/domain/Loan.java‎

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package io.github.aplotnikov.java_8_misuses.domain;
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import lombok.Data;
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import lombok.EqualsAndHashCode;
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import lombok.NoArgsConstructor;
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import lombok.ToString;
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import lombok.experimental.FieldDefaults;
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import static lombok.AccessLevel.PRIVATE;
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@NoArgsConstructor
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@ToString
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@EqualsAndHashCode
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@Data
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@FieldDefaults(level = PRIVATE)
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public class Loan {
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long id;
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Application application;
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/domain/NotificationService.java‎

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package io.github.aplotnikov.java_8_misuses.domain;
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public interface NotificationService {
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void sendSms(Client client);
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/optional/InternalOptionalUsage.java‎

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package io.github.aplotnikov.java_8_misuses.optional;
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import io.github.aplotnikov.java_8_misuses.domain.Client;
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import io.github.aplotnikov.java_8_misuses.domain.NotificationService;
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import io.github.aplotnikov.java_8_misuses.utils.Annotations.Good;
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import io.github.aplotnikov.java_8_misuses.utils.Annotations.Ugly;
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import java.util.Optional;
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import static java.util.Objects.nonNull;
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class InternalOptionalUsage {
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@Ugly
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class UnclearOptionalDependencyWithCheckForNull {
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private NotificationService notificationService;
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void process(Client client) {
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if (nonNull(notificationService)) {
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notificationService.sendSms(client);
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}
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}
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void setNotificationService(NotificationService notificationService) {
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this.notificationService = notificationService;
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}
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}
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@Good
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class ValidInternalOptionalDependency {
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private Optional<NotificationService> optionalNotificationService = Optional.empty();
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void process(Client client) {
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optionalNotificationService.ifPresent(service -> service.sendSms(client));
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}
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void setNotificationService(NotificationService notificationService) {
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optionalNotificationService = Optional.ofNullable(notificationService);
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}
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}
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/optional/OptionalConstructorParameters.java‎

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package io.github.aplotnikov.java_8_misuses.optional;
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import io.github.aplotnikov.java_8_misuses.domain.Client;
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import io.github.aplotnikov.java_8_misuses.utils.Annotations.Good;
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import io.github.aplotnikov.java_8_misuses.utils.Annotations.Ugly;
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import lombok.EqualsAndHashCode;
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import lombok.Getter;
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import lombok.ToString;
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import lombok.experimental.FieldDefaults;
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import java.util.List;
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import java.util.Optional;
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import static java.util.Arrays.asList;
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import static java.util.Objects.nonNull;
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import static lombok.AccessLevel.PRIVATE;
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class OptionalConstructorParameters {
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@Ugly
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class OptionalLeaksOutsideClass {
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List<Email> prepareEmails(Client client) {
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Email noAttachment = new Email("First!", "No attachment", Optional.empty());
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Email withAttachment = new Email("Second!", "With attachment", Optional.of(new Attachment()));
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return asList(noAttachment, withAttachment);
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}
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@FieldDefaults(makeFinal = true, level = PRIVATE)
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@Getter
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@ToString
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@EqualsAndHashCode
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class Email {
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String subject;
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String body;
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Optional<Attachment> attachment;
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Email(String subject, String body, Optional<Attachment> attachment) {
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this.subject = subject;
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this.body = body;
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this.attachment = attachment;
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}
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}
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}
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@Good
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class OverloadedConstructors {
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List<Email> prepareEmails(Client client) {
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return List.of(
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new Email("First!", "No attachment"),
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new Email("Second!", "With attachment", new Attachment())
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);
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}
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@FieldDefaults(makeFinal = true, level = PRIVATE)
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@Getter
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@ToString
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@EqualsAndHashCode
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class Email {
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String subject;
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String body;
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Attachment attachment;
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Email(String subject, String body) {
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this(subject, body, null);
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}
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Email(String subject, String body, Attachment attachment) {
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this.subject = subject;
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this.body = body;
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this.attachment = attachment;
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}
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boolean hasAttachment() {
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return nonNull(attachment);
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}
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}
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}
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class Attachment {}
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/optional/OptionalForCollections.java‎

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package io.github.aplotnikov.java_8_misuses.optional;
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import io.github.aplotnikov.java_8_misuses.domain.Client;
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import io.github.aplotnikov.java_8_misuses.domain.Loan;
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import java.util.List;
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import java.util.Optional;
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import static io.github.aplotnikov.java_8_misuses.utils.Annotations.Good;
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import static io.github.aplotnikov.java_8_misuses.utils.Annotations.Ugly;
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import static java.util.Collections.emptyList;
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class OptionalForCollections {
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@Ugly
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class TooVerbose {
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Loan findLastClientLoan(Client client) {
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Optional<List<Loan>> loans = findClientLoans(client.getId());
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if (loans.isPresent() && !loans.get().isEmpty()) {
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return loans.get().get(0);
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}
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throw new IllegalStateException("No loans were found");
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}
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private Optional<List<Loan>> findClientLoans(long id) {
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//find loans into DB
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return Optional.empty();
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}
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}
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@Good
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class NiceAndClean {
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Loan findLastClientLoan(Client client) {
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return findClientLoans(client.getId())
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.stream()
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.findFirst()
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.orElseThrow(() -> new IllegalStateException("No loans were found"));
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}
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private List<Loan> findClientLoans(long id) {
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//find loans into DB
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return emptyList();
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}
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}
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/optional/OptionalOrElse.java‎

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package io.github.aplotnikov.java_8_misuses.optional;
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import io.github.aplotnikov.java_8_misuses.domain.Client;
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import io.github.aplotnikov.java_8_misuses.domain.Loan;
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import io.github.aplotnikov.java_8_misuses.utils.Annotations.Good;
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import io.github.aplotnikov.java_8_misuses.utils.Annotations.Ugly;
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import java.util.concurrent.atomic.AtomicLong;
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import static java.util.Optional.ofNullable;
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class OptionalOrElse {
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class BeforeJava8 {
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long findLoanId(Client client) {
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return client != null && client.getLastLoan() != null ? client.getLastLoan().getId() : -1L;
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}
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}
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@Ugly
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class UsingOptionalIsPresent {
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long findLoanId(Client client) {
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if (ofNullable(client).isPresent()) {
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if (ofNullable(client.getLastLoan()).isPresent()) {
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return client.getLastLoan().getId();
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}
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}
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return -1L;
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}
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}
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@Ugly
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class UsingIfPresentInSameImperativeWayWithDirtyHackOptionalIsPresent {
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long findLoanId(Client givenClient) {
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AtomicLong result = new AtomicLong(-1);
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ofNullable(givenClient).ifPresent(
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client -> client.findLastLoan().ifPresent(
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loan -> result.set(loan.getId())
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)
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);
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return result.get();
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}
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}
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@Good
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class UsingOrElse {
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long findLoanId(Client client) {
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return ofNullable(client)
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.map(Client::getLastLoan)
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.map(Loan::getId)
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.orElse(-1L);
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}
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}
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/optional/OptionalOrThrow.java‎

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package io.github.aplotnikov.java_8_misuses.optional;
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import io.github.aplotnikov.java_8_misuses.domain.Client;
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import io.github.aplotnikov.java_8_misuses.domain.Loan;
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import io.github.aplotnikov.java_8_misuses.utils.Annotations.Good;
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import io.github.aplotnikov.java_8_misuses.utils.Annotations.Ugly;
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import java.util.Optional;
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class OptionalOrThrow {
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@Ugly
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class ManualCheckForPresenceToThrowException {
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Loan getLoan(Client client) {
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if (client.findLastLoan().isPresent()) {
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return client.findLastLoan().get();
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}
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throw new IllegalStateException("Client does not have any loans");
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}
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private Optional<Loan> findLoan(long id) {
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return Optional.empty();
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}
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void deleteLoan(long id) {
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Optional<Loan> loan = findLoan(id);
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if (loan.isPresent()) {
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delete(loan.get());
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}
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}
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private void delete(Loan loan) {
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// delete loan from DB
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}
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}
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@Good
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class OrElseThrowUsage {
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Loan getLoan(Client client) {
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return client.findLastLoan()
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.orElseThrow(() -> new IllegalStateException("Client does not have any loans"));
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}
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void deleteLoan(long id) {
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findLoan(id).ifPresent(this::delete);
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}
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private Optional<Loan> findLoan(long id) {
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return Optional.empty();
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}
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private void delete(Loan loan) {
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// delete loan from DB
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}
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}
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}

‎src/main/java/io/github/aplotnikov/java_8_misuses/optional/OptionalOverEngineering.java‎

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package io.github.aplotnikov.java_8_misuses.optional;
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import io.github.aplotnikov.java_8_misuses.domain.Loan;
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import java.util.Optional;
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import static java.util.Objects.nonNull;
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class OptionalOverEngineering {
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class NullProtectionOverEngineering {
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Loan copy(Loan loan) {
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Loan copy = new Loan();
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copy.setId(loan.getId());
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Optional.ofNullable(loan.getApplication()).ifPresent(copy::setApplication);
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return copy;
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}
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}
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class SimpleConditionalCopying {
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Loan copy(Loan loan) {
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Loan copy = new Loan();
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copy.setId(loan.getId());
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if (nonNull(loan.getApplication())) {
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copy.setApplication(loan.getApplication());
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}
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return copy;
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}
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}
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}

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