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* Create StreamFromEmptyList.java

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* Create StreamFromEmptyListUnitTest.java

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* Create README.md

Adding README file.

* Create pom.xml

* Create pom.xml

* Create REAME.md

* Delete core-java-modules/core-java-streams-6/src/README.md

* Delete core-java-modules/core-java-streams-6/src/pom.xml

* Update pom.xml

* Update pom.xml
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vaibhav007jain 2024-01-09 10:11:00 +05:30 committed by GitHub
parent c23c21e38e
commit 40dc851047
5 changed files with 172 additions and 0 deletions
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core-java-modules/core-java-streams-6/REAME.md Normal file
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core-java-modules/core-java-streams-6/pom.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-streams-6</artifactId>
<name>core-java-streams-6</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung.core-java-modules</groupId>
<artifactId>core-java-modules</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<dependencies>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>${log4j.version}</version>
</dependency>
<dependency>
<groupId>org.junit</groupId>
<artifactId>junit-bom</artifactId>
<version>${junit-jupiter.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj-core.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>${commons-lang3.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.vavr</groupId>
<artifactId>vavr</artifactId>
<version>${vavr.version}</version>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>${guava.version}</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>${commons-collections4.version}</version>
</dependency>
</dependencies>
<build>
<finalName>core-java-streams-6</finalName>
<resources>
<resource>
<directory>../core-java-streams-6/src/main</directory>
<filtering>true</filtering>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>${maven.compiler.source}</source>
<target>${maven.compiler.target}</target>
<compilerArgument>-parameters</compilerArgument>
</configuration>
</plugin>
</plugins>
</build>
<properties>
<maven.compiler.source>12</maven.compiler.source>
<maven.compiler.target>12</maven.compiler.target>
<vavr.version>0.10.2</vavr.version>
<assertj-core.version>3.23.1</assertj-core.version>
<commons-lang3.version>3.12.0</commons-lang3.version>
</properties>
</project>

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core-java-modules/core-java-streams-6/src/main/java/com/baeldung/streams/emptylists/StreamFromEmptyList.java Normal file
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package com.baeldung.streams.emptylists;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class StreamFromEmptyList {
public static void main(String[] args) {
createStreamFromEmptyList();
List<String> nameList = getList();
printNameLengths(nameList); // passing null
printNameLengths((nameList == null) ? List.of() : nameList); // passing empty list
collectStreamOfEmptyListToAnotherList();
}
private static void collectStreamOfEmptyListToAnotherList() {
List<String> emptyList = new ArrayList<>();
List<String> collectedList = emptyList.stream().collect(Collectors.toList());
System.out.println(collectedList.size() == 0);
collectedList = emptyList.stream().filter(s -> s.startsWith("a")).collect(Collectors.toList());
System.out.println(collectedList.size() == 0);
}
private static void createStreamFromEmptyList() {
List<String> emptyList = new ArrayList<>();
Stream<String> emptyStream = emptyList.stream();
System.out.println(emptyStream.findAny().isEmpty());
}
private static void printNameLengths(List<String> nameList) {
// Without Stream - Traditional approach with null check
if (nameList != null) {
for (String name : nameList) {
System.out.println("Length of " + name + ": " + name.length());
}
} else {
System.out.println("List is null. Unable to process.");
}
// With Stream - More concise approach
Optional.ofNullable(nameList).ifPresent(list -> list.stream()
.map(name -> "Length of " + name + ": " + name.length()).forEach(System.out::println));
}
private static List<String> getList() {
// This method may return null for demonstration purposes
return null;
}
}

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core-java-modules/core-java-streams-6/src/test/java/com/baeldung/streams/emptylists/StreamFromEmptyListUnitTest.java Normal file
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package com.baeldung.streams.emptylists;
import static org.junit.Assert.assertTrue;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.junit.Test;
public class StreamFromEmptyListUnitTest {
@Test
public void givenEmptyList_whenConvertedToStream_thenResultantStreamIsEmpty() {
List<String> emptyList = new ArrayList<>();
Stream<String> emptyStream = emptyList.stream();
assertTrue(emptyStream.findAny().isEmpty());
}
@Test
public void givenEmptyList_whenCollectStreamOfEmptyListToAnotherList_thenResultantListIsEmpty() {
List<String> emptyList = new ArrayList<>();
List<String> collectedList = emptyList.stream().collect(Collectors.toList());
assertTrue(collectedList.isEmpty());
}
}

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core-java-modules/pom.xml
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<module>core-java-perf-2</module>
<module>core-java-streams-4</module>
<module>core-java-streams-5</module>
<module>core-java-streams-6</module>
<module>core-java-streams-collect</module>
<module>core-java-streams-maps</module>
<module>core-java-string-operations-3</module>