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BAEL-4588: Update Guide To Java 8 Optional (#9995)

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* BAEL-4588: Fix maven-shade-plugin version

* BAEL-4588: Add empty core-java-11-2 module structure

* BAEL-4588: Move Guide To Java 8 Optional to core-java-11-2

* BAEL-4588: Add Java 10 orElseThrow() example
This commit is contained in:
kwoyke
2020-09-09 18:35:31 +02:00
committed by GitHub
parent 21845f38ee
commit 3a97034b6a
8 changed files with 68 additions and 4 deletions
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1
core-java-modules/core-java-optional/README.md
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@@ -4,7 +4,6 @@ This module contains articles about Java Optional.
### Relevant Articles:
- [Java Optional as Return Type](https://www.baeldung.com/java-optional-return)
- [Guide to Java 8 Optional](https://www.baeldung.com/java-optional)
- [Java Optional – orElse() vs orElseGet()](https://www.baeldung.com/java-optional-or-else-vs-or-else-get)
- [Transforming an Empty String into an Empty Optional](https://www.baeldung.com/java-empty-string-to-empty-optional)
- [Filtering a Stream of Optionals in Java](https://www.baeldung.com/java-filter-stream-of-optional)

13
core-java-modules/core-java-optional/src/main/java/com/baeldung/optional/Modem.java
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@@ -1,13 +0,0 @@
package com.baeldung.optional;
public class Modem {
private Double price;
public Modem(Double price) {
this.price = price;
}
public Double getPrice() {
return price;
}
}

74
core-java-modules/core-java-optional/src/main/java/com/baeldung/optional/Person.java
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@@ -1,74 +0,0 @@
package com.baeldung.optional;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;
public class Person {
private String name;
private int age;
private String password;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public Optional<String> getName() {
return Optional.ofNullable(name);
}
public void setName(String name) {
this.name = name;
}
public Optional<Integer> getAge() {
return Optional.of(age);
}
public void setAge(int age) {
this.age = age;
}
public void setPassword(String password) {
this.password = password;
}
public Optional<String> getPassword() {
return Optional.ofNullable(password);
}
public static List<Person> search(List<Person> people, String name, Optional<Integer> age) {
// Null checks for people and name
return people.stream()
.filter(p -> p.getName().equals(name))
.filter(p -> p.getAge().get() >= age.orElse(0))
.collect(Collectors.toList());
}
public static List<Person> search(List<Person> people, String name, Integer age) {
// Null checks for people and name
final Integer ageFilter = age != null ? age : 0;
return people.stream()
.filter(p -> p.getName().equals(name))
.filter(p -> p.getAge().get() >= ageFilter)
.collect(Collectors.toList());
}
public static List<Person> search(List<Person> people, String name) {
return doSearch(people, name, 0);
}
public static List<Person> search(List<Person> people, String name, int age) {
return doSearch(people, name, age);
}
private static List<Person> doSearch(List<Person> people, String name, int age) {
// Null checks for people and name
return people.stream()
.filter(p -> p.getName().equals(name))
.filter(p -> p.getAge().get().intValue() >= age)
.collect(Collectors.toList());
}
}

110
core-java-modules/core-java-optional/src/test/java/com/baeldung/optional/OptionalChainingUnitTest.java
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@@ -1,110 +0,0 @@
package com.baeldung.optional;
import org.junit.Before;
import org.junit.Test;
import java.util.Optional;
import java.util.function.Supplier;
import java.util.stream.Stream;
import static org.junit.Assert.*;
public class OptionalChainingUnitTest {
private boolean getEmptyEvaluated;
private boolean getHelloEvaluated;
private boolean getByeEvaluated;
@Before
public void setUp() {
getEmptyEvaluated = false;
getHelloEvaluated = false;
getByeEvaluated = false;
}
@Test
public void givenThreeOptionals_whenChaining_thenFirstNonEmptyIsReturned() {
Optional<String> found = Stream.of(getEmpty(), getHello(), getBye())
.filter(Optional::isPresent)
.map(Optional::get)
.findFirst();
assertEquals(getHello(), found);
}
@Test
public void givenTwoEmptyOptionals_whenChaining_thenEmptyOptionalIsReturned() {
Optional<String> found = Stream.of(getEmpty(), getEmpty())
.filter(Optional::isPresent)
.map(Optional::get)
.findFirst();
assertFalse(found.isPresent());
}
@Test
public void givenTwoEmptyOptionals_whenChaining_thenDefaultIsReturned() {
String found = Stream.<Supplier<Optional<String>>>of(
() -> createOptional("empty"),
() -> createOptional("empty")
)
.map(Supplier::get)
.filter(Optional::isPresent)
.map(Optional::get)
.findFirst()
.orElseGet(() -> "default");
assertEquals("default", found);
}
@Test
public void givenThreeOptionals_whenChaining_thenFirstNonEmptyIsReturnedAndRestNotEvaluated() {
Optional<String> found = Stream.<Supplier<Optional<String>>>of(this::getEmpty, this::getHello, this::getBye)
.map(Supplier::get)
.filter(Optional::isPresent)
.map(Optional::get)
.findFirst();
assertTrue(this.getEmptyEvaluated);
assertTrue(this.getHelloEvaluated);
assertFalse(this.getByeEvaluated);
assertEquals(getHello(), found);
}
@Test
public void givenTwoOptionalsReturnedByOneArgMethod_whenChaining_thenFirstNonEmptyIsReturned() {
Optional<String> found = Stream.<Supplier<Optional<String>>>of(
() -> createOptional("empty"),
() -> createOptional("hello")
)
.map(Supplier::get)
.filter(Optional::isPresent)
.map(Optional::get)
.findFirst();
assertEquals(createOptional("hello"), found);
}
private Optional<String> getEmpty() {
this.getEmptyEvaluated = true;
return Optional.empty();
}
private Optional<String> getHello() {
this.getHelloEvaluated = true;
return Optional.of("hello");
}
private Optional<String> getBye() {
this.getByeEvaluated = true;
return Optional.of("bye");
}
private Optional<String> createOptional(String input) {
if (input == null || "".equals(input) || "empty".equals(input)) {
return Optional.empty();
}
return Optional.of(input);
}
}

280
core-java-modules/core-java-optional/src/test/java/com/baeldung/optional/OptionalUnitTest.java
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@@ -1,280 +0,0 @@
package com.baeldung.optional;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Arrays;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Optional;
import static org.junit.Assert.*;
public class OptionalUnitTest {
private static final Logger LOG = LoggerFactory.getLogger(OptionalUnitTest.class);
// creating Optional
@Test
public void whenCreatesEmptyOptional_thenCorrect() {
Optional<String> empty = Optional.empty();
assertFalse(empty.isPresent());
}
@Test
public void givenNonNull_whenCreatesNonNullable_thenCorrect() {
String name = "baeldung";
Optional<String> opt = Optional.of(name);
assertTrue(opt.isPresent());
}
@Test(expected = NullPointerException.class)
public void givenNull_whenThrowsErrorOnCreate_thenCorrect() {
String name = null;
Optional.of(name);
}
@Test
public void givenNonNull_whenCreatesOptional_thenCorrect() {
String name = "baeldung";
Optional<String> opt = Optional.of(name);
assertTrue(opt.isPresent());
}
@Test
public void givenNonNull_whenCreatesNullable_thenCorrect() {
String name = "baeldung";
Optional<String> opt = Optional.ofNullable(name);
assertTrue(opt.isPresent());
}
@Test
public void givenNull_whenCreatesNullable_thenCorrect() {
String name = null;
Optional<String> opt = Optional.ofNullable(name);
assertFalse(opt.isPresent());
}
// Checking Value With isPresent()
@Test
public void givenOptional_whenIsPresentWorks_thenCorrect() {
Optional<String> opt = Optional.of("Baeldung");
assertTrue(opt.isPresent());
opt = Optional.ofNullable(null);
assertFalse(opt.isPresent());
}
// Condition Action With ifPresent()
@Test
public void givenOptional_whenIfPresentWorks_thenCorrect() {
Optional<String> opt = Optional.of("baeldung");
opt.ifPresent(name -> LOG.debug("{}", name.length()));
}
// returning Value With get()
@Test
public void givenOptional_whenGetsValue_thenCorrect() {
Optional<String> opt = Optional.of("baeldung");
String name = opt.get();
assertEquals("baeldung", name);
}
@Test(expected = NoSuchElementException.class)
public void givenOptionalWithNull_whenGetThrowsException_thenCorrect() {
Optional<String> opt = Optional.ofNullable(null);
String name = opt.get();
}
@Test
public void givenAnEmptyOptional_thenIsEmptyBehavesAsExpected() {
Optional<String> opt = Optional.of("Baeldung");
assertTrue(opt.isPresent());
opt = Optional.ofNullable(null);
assertFalse(opt.isPresent());
}
// Conditional Return With filter()
@Test
public void whenOptionalFilterWorks_thenCorrect() {
Integer year = 2016;
Optional<Integer> yearOptional = Optional.of(year);
boolean is2016 = yearOptional.filter(y -> y == 2016)
.isPresent();
assertTrue(is2016);
boolean is2017 = yearOptional.filter(y -> y == 2017)
.isPresent();
assertFalse(is2017);
}
@Test
public void whenFiltersWithoutOptional_thenCorrect() {
assertTrue(priceIsInRange1(new Modem(10.0)));
assertFalse(priceIsInRange1(new Modem(9.9)));
assertFalse(priceIsInRange1(new Modem(null)));
assertFalse(priceIsInRange1(new Modem(15.5)));
assertFalse(priceIsInRange1(null));
}
@Test
public void whenFiltersWithOptional_thenCorrect() {
assertTrue(priceIsInRange2(new Modem(10.0)));
assertFalse(priceIsInRange2(new Modem(9.9)));
assertFalse(priceIsInRange2(new Modem(null)));
assertFalse(priceIsInRange2(new Modem(15.5)));
assertFalse(priceIsInRange1(null));
}
public boolean priceIsInRange1(Modem modem) {
boolean isInRange = false;
if (modem != null && modem.getPrice() != null && (modem.getPrice() >= 10 && modem.getPrice() <= 15)) {
isInRange = true;
}
return isInRange;
}
public boolean priceIsInRange2(Modem modem2) {
return Optional.ofNullable(modem2)
.map(Modem::getPrice)
.filter(p -> p >= 10)
.filter(p -> p <= 15)
.isPresent();
}
// Transforming Value With map()
@Test
public void givenOptional_whenMapWorks_thenCorrect() {
List<String> companyNames = Arrays.asList("paypal", "oracle", "", "microsoft", "", "apple");
Optional<List<String>> listOptional = Optional.of(companyNames);
int size = listOptional.map(List::size)
.orElse(0);
assertEquals(6, size);
}
@Test
public void givenOptional_whenMapWorks_thenCorrect2() {
String name = "baeldung";
Optional<String> nameOptional = Optional.of(name);
int len = nameOptional.map(String::length)
.orElse(0);
assertEquals(8, len);
}
@Test
public void givenOptional_whenMapWorksWithFilter_thenCorrect() {
String password = " password ";
Optional<String> passOpt = Optional.of(password);
boolean correctPassword = passOpt.filter(pass -> pass.equals("password"))
.isPresent();
assertFalse(correctPassword);
correctPassword = passOpt.map(String::trim)
.filter(pass -> pass.equals("password"))
.isPresent();
assertTrue(correctPassword);
}
// Transforming Value With flatMap()
@Test
public void givenOptional_whenFlatMapWorks_thenCorrect2() {
Person person = new Person("john", 26);
Optional<Person> personOptional = Optional.of(person);
Optional<Optional<String>> nameOptionalWrapper = personOptional.map(Person::getName);
Optional<String> nameOptional = nameOptionalWrapper.orElseThrow(IllegalArgumentException::new);
String name1 = nameOptional.orElseThrow(IllegalArgumentException::new);
assertEquals("john", name1);
String name = personOptional.flatMap(Person::getName)
.orElseThrow(IllegalArgumentException::new);
assertEquals("john", name);
}
@Test
public void givenOptional_whenFlatMapWorksWithFilter_thenCorrect() {
Person person = new Person("john", 26);
person.setPassword("password");
Optional<Person> personOptional = Optional.of(person);
String password = personOptional.flatMap(Person::getPassword)
.filter(cleanPass -> cleanPass.equals("password"))
.orElseThrow(IllegalArgumentException::new);
assertEquals("password", password);
}
// Default Value With orElse
@Test
public void whenOrElseWorks_thenCorrect() {
String nullName = null;
String name = Optional.ofNullable(nullName)
.orElse("john");
assertEquals("john", name);
}
// Default Value With orElseGet
@Test
public void whenOrElseGetWorks_thenCorrect() {
String nullName = null;
String name = Optional.ofNullable(nullName)
.orElseGet(() -> "john");
assertEquals("john", name);
}
@Test
public void whenOrElseGetAndOrElseOverlap_thenCorrect() {
String text = null;
LOG.debug("Using orElseGet:");
String defaultText = Optional.ofNullable(text)
.orElseGet(this::getMyDefault);
assertEquals("Default Value", defaultText);
LOG.debug("Using orElse:");
defaultText = Optional.ofNullable(text)
.orElse(getMyDefault());
assertEquals("Default Value", defaultText);
}
@Test
public void whenOrElseGetAndOrElseDiffer_thenCorrect() {
String text = "Text present";
LOG.debug("Using orElseGet:");
String defaultText = Optional.ofNullable(text)
.orElseGet(this::getMyDefault);
assertEquals("Text present", defaultText);
LOG.debug("Using orElse:");
defaultText = Optional.ofNullable(text)
.orElse(getMyDefault());
assertEquals("Text present", defaultText);
}
// Exceptions With orElseThrow
@Test(expected = IllegalArgumentException.class)
public void whenOrElseThrowWorks_thenCorrect() {
String nullName = null;
String name = Optional.ofNullable(nullName)
.orElseThrow(IllegalArgumentException::new);
}
public String getMyDefault() {
LOG.debug("Getting default value...");
return "Default Value";
}
// Uncomment code when code base is compatible with Java 11
// @Test
// public void givenAnEmptyOptional_thenIsEmptyBehavesAsExpected() {
// Optional<String> opt = Optional.of("Baeldung");
// assertFalse(opt.isEmpty());
//
// opt = Optional.ofNullable(null);
// assertTrue(opt.isEmpty());
// }
}