OptionalTest.java

package com.gdn.rnd.codingguideline;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.junit.Test;

import java.util.Optional;

/**
 * @author Eko Kurniawan Khannedy
 */
public class OptionalTest {

  private Customer customer;

  @Test
  public void nameUsingIf() {
    String name = customer.getName();
    if (name == null) {
      name = "";
    }

    System.out.println(name);
  }

  @Test
  public void nameUsingOptional() {
    String name = Optional.ofNullable(customer.getName())
        .orElse("");

    System.out.println(name);
  }

  @Test
  public void dbLogicUsingIf() {

    Customer user = findCustomerById("id");
    if (user == null) {
      user = createNewUser("id");
    }

    System.out.println(user);
  }

  @Test
  public void dbLogicUsingOptional() {
    Customer user = Optional.ofNullable(findCustomerById("id"))
        .orElse(createNewUser("id"));

    System.out.println(user);
  }

  @Test
  public void nameUpperCaseUsingIf() {
    String nameUpper = customer.getName();
    if (nameUpper != null) {
      nameUpper = nameUpper.toUpperCase();
    } else {
      nameUpper = "";
    }

    System.out.println(nameUpper);
  }

  @Test
  public void nameUpperUsingOptional() {
    String nameUpper = Optional.ofNullable(customer.getName())
        .map(String::toUpperCase)
        .orElse("");

    System.out.println(nameUpper);
  }

  @Test
  public void countryUsingIf() {
    String country = "Indonesia";
    if (customer.getAddress() != null) {
      if (customer.getAddress().getCountry() != null) {
        country = customer.getAddress().getCountry();
      }
    }

    System.out.println(country);
  }

  @Test
  public void countryUsingOption() {
    String country = Optional.ofNullable(customer.getAddress())
        .map(Customer.Address::getCountry)
        .orElse("Indonesia");

    System.out.println(country);
  }

  @Test
  public void nameExceptionUsingIf() {
    String name = customer.getName();
    if (name == null) {
      throw new IllegalArgumentException("Name is null");
    }

    System.out.println(name);
  }

  @Test
  public void nameExceptionUsingOption() {
    String name = Optional.ofNullable(customer.getName())
        .orElseThrow(() -> new IllegalArgumentException("Name is null"));

    System.out.println(name);
  }

  @Test
  public void countryDoSomeThingUsingIf() {
    if (customer.getAddress() != null) {
      if (customer.getAddress().getCountry() != null) {

        // do something
        System.out.println(customer.getAddress().getCountry());

      }
    }
  }

  @Test
  public void countryDoSomethingUsingOption() {
    Optional.ofNullable(customer.getAddress())
        .map(Customer.Address::getCountry)
        .ifPresent(country -> {
          // do something
          System.out.println(customer.getAddress().getCountry());
        });
  }

  @Test
  public void nestedObjectUsingIf() {

    Long cashBalance = 0L;

    if (customer.getWallet() != null) {
      if (customer.getWallet().getBalance() != null) {
        cashBalance = customer.getWallet().getBalance().getCashBalance();
      }
    }

    System.out.println(cashBalance);
  }

  @Test
  public void nestedObjectUsingOption() {
    Long cashBalance = Optional.ofNullable(customer.getWallet())
        .map(Customer.Wallet::getBalance)
        .map(Customer.WalletBalance::getCashBalance)
        .orElse(0L);

    System.out.println(cashBalance);
  }

  @Test
  public void filterWithIf() {

    Long bonus = 0L;
    if (Customer.Type.PREMIUM.equals(customer.getType())) {
      if (customer.getWallet() != null) {
        if (customer.getWallet().getBalance() != null) {
          bonus = customer.getWallet().getBalance().getCashBalance() * 10 / 100;
        }
      }
    }

    System.out.println(bonus);
  }

  @Test
  public void filterWithOptional() {
    Long bonus = Optional.of(customer)
        .filter(value -> Customer.Type.PREMIUM.equals(value.getType()))
        .map(Customer::getWallet)
        .map(Customer.Wallet::getBalance)
        .map(balance -> balance.getCashBalance() * 10 / 100)
        .orElse(0L);

    System.out.println(bonus);
  }

  private Customer createNewUser(String id) {
    return null;
  }

  private Customer findCustomerById(String id) {
    return null;
  }

  @Builder
  @AllArgsConstructor
  @NoArgsConstructor
  @Data
  public static class Customer {

    private String name;

    private Address address;

    private Wallet wallet;

    private Type type;

    public static enum Type {
      GOLD, PREMIUM, CLASSIC
    }

    @Builder
    @AllArgsConstructor
    @NoArgsConstructor
    @Data
    public static class Address {

      private String street;

      private String city;

      private String country;

    }

    @Builder
    @AllArgsConstructor
    @NoArgsConstructor
    @Data
    public static class Wallet {

      private Long totalBalance;

      private WalletBalance balance;

    }

    @Builder
    @AllArgsConstructor
    @NoArgsConstructor
    @Data
    public static class WalletBalance {

      private Long refundBalance;

      private Long nonCashBalance;

      private Long cashBalance;

    }

  }

}