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## Core Java 11
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## Java 11 核心（Core Java 11）
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This module contains articles about Java 11 core features
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本模块中包含有关 Java 11 核心新增功能的的一些文章
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### Relevant articles
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### 相关文章
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- [Guide to Java 8 Optional](https://www.baeldung.com/java-optional)
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- [Guide to Java Reflection](http://www.baeldung.com/java-reflection)
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- [Guide to Java 8’s Collectors](https://www.baeldung.com/java-8-collectors)
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@ -9,10 +9,15 @@ import java.util.List;
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import java.util.NoSuchElementException;
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import java.util.Optional;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertFalse;
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import static org.junit.Assert.assertTrue;
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import static org.junit.Assert.*;
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/**
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* Test for Java Optional
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*
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* <p><a href="https://www.ossez.com/t/java-8-optional/13964">https://www.ossez.com/t/java-8-optional/13964</a></p>
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*
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* @author YuCheng
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*/
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public class OptionalUnitTest {
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private static final Logger LOG = LoggerFactory.getLogger(OptionalUnitTest.class);
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@ -26,7 +31,7 @@ public class OptionalUnitTest {
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@Test
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public void givenNonNull_whenCreatesNonNullable_thenCorrect() {
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String name = "baeldung";
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String name = "HoneyMoose";
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Optional<String> opt = Optional.of(name);
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assertTrue(opt.isPresent());
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}
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@ -39,14 +44,14 @@ public class OptionalUnitTest {
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@Test
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public void givenNonNull_whenCreatesOptional_thenCorrect() {
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String name = "baeldung";
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String name = "HoneyMoose";
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Optional<String> opt = Optional.of(name);
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assertTrue(opt.isPresent());
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}
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@Test
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public void givenNonNull_whenCreatesNullable_thenCorrect() {
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String name = "baeldung";
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String name = "HoneyMoose";
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Optional<String> opt = Optional.ofNullable(name);
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assertTrue(opt.isPresent());
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}
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@ -61,7 +66,7 @@ public class OptionalUnitTest {
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@Test
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public void givenOptional_whenIsPresentWorks_thenCorrect() {
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Optional<String> opt = Optional.of("Baeldung");
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Optional<String> opt = Optional.of("HoneyMoose");
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assertTrue(opt.isPresent());
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opt = Optional.ofNullable(null);
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@ -88,12 +93,12 @@ public class OptionalUnitTest {
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Optional<String> opt = Optional.ofNullable(null);
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String name = opt.get();
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}
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@Test
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public void givenAnEmptyOptional_thenIsEmptyBehavesAsExpected() {
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Optional<String> opt = Optional.of("Baeldung");
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assertTrue(opt.isPresent());
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opt = Optional.ofNullable(null);
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assertFalse(opt.isPresent());
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}
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@ -103,11 +108,9 @@ public class OptionalUnitTest {
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public void whenOptionalFilterWorks_thenCorrect() {
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Integer year = 2016;
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Optional<Integer> yearOptional = Optional.of(year);
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boolean is2016 = yearOptional.filter(y -> y == 2016)
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.isPresent();
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boolean is2016 = yearOptional.filter(y -> y == 2016).isPresent();
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assertTrue(is2016);
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boolean is2017 = yearOptional.filter(y -> y == 2017)
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.isPresent();
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boolean is2017 = yearOptional.filter(y -> y == 2017).isPresent();
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assertFalse(is2017);
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}
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@ -139,11 +142,7 @@ public class OptionalUnitTest {
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}
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public boolean priceIsInRange2(Modem modem2) {
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return Optional.ofNullable(modem2)
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.map(Modem::getPrice)
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.filter(p -> p >= 10)
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.filter(p -> p <= 15)
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.isPresent();
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return Optional.ofNullable(modem2).map(Modem::getPrice).filter(p -> p >= 10).filter(p -> p <= 15).isPresent();
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}
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// Transforming Value With map()
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@ -152,8 +151,7 @@ public class OptionalUnitTest {
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List<String> companyNames = Arrays.asList("paypal", "oracle", "", "microsoft", "", "apple");
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Optional<List<String>> listOptional = Optional.of(companyNames);
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int size = listOptional.map(List::size)
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.orElse(0);
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int size = listOptional.map(List::size).orElse(0);
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assertEquals(6, size);
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}
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@ -162,8 +160,7 @@ public class OptionalUnitTest {
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String name = "baeldung";
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Optional<String> nameOptional = Optional.of(name);
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int len = nameOptional.map(String::length)
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.orElse(0);
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int len = nameOptional.map(String::length).orElse(0);
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assertEquals(8, len);
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}
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@ -171,13 +168,10 @@ public class OptionalUnitTest {
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public void givenOptional_whenMapWorksWithFilter_thenCorrect() {
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String password = " password ";
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Optional<String> passOpt = Optional.of(password);
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boolean correctPassword = passOpt.filter(pass -> pass.equals("password"))
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.isPresent();
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boolean correctPassword = passOpt.filter(pass -> pass.equals("password")).isPresent();
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assertFalse(correctPassword);
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correctPassword = passOpt.map(String::trim)
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.filter(pass -> pass.equals("password"))
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.isPresent();
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correctPassword = passOpt.map(String::trim).filter(pass -> pass.equals("password")).isPresent();
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assertTrue(correctPassword);
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}
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@ -192,8 +186,7 @@ public class OptionalUnitTest {
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String name1 = nameOptional.orElseThrow(IllegalArgumentException::new);
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assertEquals("john", name1);
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String name = personOptional.flatMap(Person::getName)
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.orElseThrow(IllegalArgumentException::new);
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String name = personOptional.flatMap(Person::getName).orElseThrow(IllegalArgumentException::new);
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assertEquals("john", name);
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}
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@ -203,9 +196,7 @@ public class OptionalUnitTest {
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person.setPassword("password");
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Optional<Person> personOptional = Optional.of(person);
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String password = personOptional.flatMap(Person::getPassword)
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.filter(cleanPass -> cleanPass.equals("password"))
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.orElseThrow(IllegalArgumentException::new);
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String password = personOptional.flatMap(Person::getPassword).filter(cleanPass -> cleanPass.equals("password")).orElseThrow(IllegalArgumentException::new);
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assertEquals("password", password);
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}
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@ -213,8 +204,7 @@ public class OptionalUnitTest {
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@Test
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public void whenOrElseWorks_thenCorrect() {
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String nullName = null;
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String name = Optional.ofNullable(nullName)
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.orElse("john");
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String name = Optional.ofNullable(nullName).orElse("john");
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assertEquals("john", name);
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}
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@ -222,8 +212,7 @@ public class OptionalUnitTest {
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@Test
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public void whenOrElseGetWorks_thenCorrect() {
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String nullName = null;
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String name = Optional.ofNullable(nullName)
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.orElseGet(() -> "john");
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String name = Optional.ofNullable(nullName).orElseGet(() -> "john");
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assertEquals("john", name);
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}
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@ -232,13 +221,11 @@ public class OptionalUnitTest {
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public void whenOrElseGetAndOrElseOverlap_thenCorrect() {
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String text = null;
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LOG.debug("Using orElseGet:");
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String defaultText = Optional.ofNullable(text)
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.orElseGet(this::getMyDefault);
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String defaultText = Optional.ofNullable(text).orElseGet(this::getMyDefault);
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assertEquals("Default Value", defaultText);
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LOG.debug("Using orElse:");
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defaultText = Optional.ofNullable(text)
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.orElse(getMyDefault());
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defaultText = Optional.ofNullable(text).orElse(getMyDefault());
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assertEquals("Default Value", defaultText);
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}
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@ -246,13 +233,11 @@ public class OptionalUnitTest {
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public void whenOrElseGetAndOrElseDiffer_thenCorrect() {
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String text = "Text present";
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LOG.debug("Using orElseGet:");
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String defaultText = Optional.ofNullable(text)
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.orElseGet(this::getMyDefault);
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String defaultText = Optional.ofNullable(text).orElseGet(this::getMyDefault);
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assertEquals("Text present", defaultText);
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LOG.debug("Using orElse:");
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defaultText = Optional.ofNullable(text)
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.orElse(getMyDefault());
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defaultText = Optional.ofNullable(text).orElse(getMyDefault());
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assertEquals("Text present", defaultText);
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}
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@ -260,8 +245,7 @@ public class OptionalUnitTest {
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@Test(expected = IllegalArgumentException.class)
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public void whenOrElseThrowWorks_thenCorrect() {
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String nullName = null;
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String name = Optional.ofNullable(nullName)
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.orElseThrow(IllegalArgumentException::new);
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String name = Optional.ofNullable(nullName).orElseThrow(IllegalArgumentException::new);
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}
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@Test(expected = NoSuchElementException.class)
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@ -274,7 +258,7 @@ public class OptionalUnitTest {
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LOG.debug("Getting default value...");
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return "Default Value";
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}
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// Uncomment code when code base is compatible with Java 11
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// @Test
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// public void givenAnEmptyOptional_thenIsEmptyBehavesAsExpected() {
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