diff --git a/core-java-modules/core-java-streams-5/pom.xml b/core-java-modules/core-java-streams-5/pom.xml index e217271f4c..33cd69f761 100644 --- a/core-java-modules/core-java-streams-5/pom.xml +++ b/core-java-modules/core-java-streams-5/pom.xml @@ -48,6 +48,11 @@ guava ${guava.version} + + org.apache.commons + commons-collections4 + ${commons-collections4.version} + diff --git a/core-java-modules/core-java-streams-5/src/main/java/com/baeldung/streams/firstmatchingelement/User.java b/core-java-modules/core-java-streams-5/src/main/java/com/baeldung/streams/firstmatchingelement/User.java new file mode 100644 index 0000000000..cb29af529a --- /dev/null +++ b/core-java-modules/core-java-streams-5/src/main/java/com/baeldung/streams/firstmatchingelement/User.java @@ -0,0 +1,21 @@ +package com.baeldung.streams.firstmatchingelement; + +public class User { + + private String userName; + private Integer userId; + + public User(Integer userId, String userName) { + this.userId = userId; + this.userName = userName; + } + + public String getUserName() { + return userName; + } + + public Integer getUserId() { + return userId; + } + +} diff --git a/core-java-modules/core-java-streams-5/src/test/java/com/baeldung/streams/firstmatchingelement/FirstMatchingElementUnitTest.java b/core-java-modules/core-java-streams-5/src/test/java/com/baeldung/streams/firstmatchingelement/FirstMatchingElementUnitTest.java new file mode 100644 index 0000000000..db9415e94b --- /dev/null +++ b/core-java-modules/core-java-streams-5/src/test/java/com/baeldung/streams/firstmatchingelement/FirstMatchingElementUnitTest.java @@ -0,0 +1,72 @@ +package com.baeldung.streams.firstmatchingelement; + + +import static org.junit.Assert.assertEquals; + +import java.util.List; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.stream.IntStream; + +import org.apache.commons.collections4.IterableUtils; +import org.junit.Test; + +import com.google.common.collect.Iterables; + +public class FirstMatchingElementUnitTest { + + private List userList = List.of(new User(1, "David"), new User(2, "John"), new User(3, "Roger"), new User(4, "John")); + private String searchName = "John"; + + @Test + public void whenUsingStream_thenFindFirstMatchingUserIndex() { + AtomicInteger counter = new AtomicInteger(-1); + int index = userList.stream() + .filter(user -> { + counter.getAndIncrement(); + return searchName.equals(user.getUserName()); + }) + .mapToInt(user -> counter.get()) + .findFirst() + .orElse(-1); + + assertEquals(1, index); + } + + @Test + public void whenUsingIntStream_thenFindFirstMatchingUserIndex() { + int index = IntStream.range(0, userList.size() - 1) + .filter(streamIndex -> searchName.equals(userList.get(streamIndex).getUserName())) + .findFirst() + .orElse(-1); + assertEquals(1, index); + } + + @Test + public void whenUsingTakeWhile_thenFindFirstMatchingUserIndex() { + long predicateIndex = userList.stream() + .takeWhile(user -> !user.getUserName().equals(searchName)) + .count(); + assertEquals(1, predicateIndex); + } + + @Test + public void whenUsingTakeWhile_thenFindIndexFromNoMatchingElement() { + List userList = List.of(new User(1, "David"), new User(2, "Vick"), new User(3, "Roger"), new User(4, "James")); + long predicateIndex = userList.stream() + .takeWhile(user -> !user.getUserName().equals(searchName)) + .count(); + assertEquals(4, predicateIndex); + } + + @Test + public void whenUsingGoogleGuava_thenFindFirstMatchingUserIndex() { + int index = Iterables.indexOf(userList, user -> searchName.equals(user.getUserName())); + assertEquals(1, index); + } + + @Test + public void whenUsingApacheCommons_thenFindFirstMatchingUserIndex() { + int index = IterableUtils.indexOf(userList, user -> searchName.equals(user.getUserName())); + assertEquals(1, index); + } +}