BAEL-833: How to get last element of a Stream in Java? (#1930)

* Different Types of Bean Injection in Spring

* Fixed code formatting and test names for "Different Types of Bean Injection in Spring"

* BAEL-833: How to get last element of a Stream in Java?

* BAEL-833: Updated based on review from editor

core-java/src/main/java/com/baeldung/stream/StreamApi.java

@@ -0,0 +1,24 @@
+package com.baeldung.stream;
+
+import java.util.List;
+import java.util.stream.Stream;
+
+public class StreamApi {
+
+    public String getLastElementUsingReduce(List<String> valueList) {
+        Stream<String> stream = valueList.stream();
+        return stream.reduce((first, second) -> second).orElse(null);
+    }
+    
+    public Integer getInfiniteStreamLastElementUsingReduce() {
+        Stream<Integer> stream = Stream.iterate(0, i -> i + 1);
+        return stream.limit(20).reduce((first, second) -> second).orElse(null);
+    }
+    
+    public String getLastElementUsingSkip(List<String> valueList) {
+        long count = valueList.stream().count();
+        Stream<String> stream = valueList.stream();
+        return stream.skip(count - 1).findFirst().orElse(null);
+    }
+
+}

core-java/src/test/java/com/baeldung/stream/StreamApiTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.stream;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+
+public class StreamApiTest {
+    private StreamApi streamApi = new StreamApi();
+
+    @Test
+    public void givenList_whenGetLastElementUsingReduce_thenReturnLastElement() {
+        List<String> valueList = new ArrayList<String>();
+        valueList.add("Joe");
+        valueList.add("John");
+        valueList.add("Sean");
+
+        String last = streamApi.getLastElementUsingReduce(valueList);
+
+        assertEquals("Sean", last);
+    }
+    
+    @Test
+    public void givenInfiniteStream_whenGetInfiniteStreamLastElementUsingReduce_thenReturnLastElement() {
+        Integer last = streamApi.getInfiniteStreamLastElementUsingReduce();
+        assertEquals(new Integer(19), last);
+    }
+    
+    @Test
+    public void givenListAndCount_whenGetLastElementUsingSkip_thenReturnLastElement() {
+        List<String> valueList = new ArrayList<String>();
+        valueList.add("Joe");
+        valueList.add("John");
+        valueList.add("Sean");
+
+        String last = streamApi.getLastElementUsingSkip(valueList);
+
+        assertEquals("Sean", last);
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjection/FileReader.java

@@ -0,0 +1,19 @@
+package com.baeldung.beaninjection;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class FileReader {
+
+    @Autowired
+    private Location location;
+
+    public Location getLocation() {
+        return location;
+    }
+
+    public void setLocation(Location location) {
+        this.location = location;
+    }
+}

spring-core/src/main/java/com/baeldung/beaninjection/FtpReader.java

@@ -0,0 +1,28 @@
+package com.baeldung.beaninjection;
+
+public class FtpReader {
+    private String ftpHost = null;
+    private Integer ftpPort = null;
+
+    // Constructor with arguments
+    public FtpReader(String host, Integer port) {
+        this.ftpHost = host;
+        this.ftpPort = port;
+    }
+
+    public String getFtpHost() {
+        return ftpHost;
+    }
+
+    public void setFtpHost(String ftpHost) {
+        this.ftpHost = ftpHost;
+    }
+
+    public Integer getFtpPort() {
+        return ftpPort;
+    }
+
+    public void setFtpPort(Integer ftpPort) {
+        this.ftpPort = ftpPort;
+    }
+}

spring-core/src/main/java/com/baeldung/beaninjection/Location.java

@@ -0,0 +1,17 @@
+package com.baeldung.beaninjection;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Location {
+    private String filePath;
+
+    public String getFilePath() {
+        return filePath;
+    }
+
+    public void setFilePath(String filePath) {
+        this.filePath = filePath;
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjection/ReaderApplicationConfig.java

@@ -0,0 +1,15 @@
+package com.baeldung.beaninjection;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan(basePackages = { "com.baeldung.beaninjection" })
+public class ReaderApplicationConfig {
+
+    @Bean
+    public FtpReader exampleDAO() {
+        return new FtpReader("localhost", 21);
+    }
+}

spring-core/src/main/java/com/baeldung/beaninjection/ReaderManager.java

@@ -0,0 +1,33 @@
+package com.baeldung.beaninjection;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class ReaderManager {
+    private FileReader fileReader;
+    private FtpReader ftpReader;
+
+    @Autowired
+    public ReaderManager(FtpReader ftpReader) {
+        this.ftpReader = ftpReader;
+    }
+
+    @Autowired
+    public void setFileReader(FileReader fileReader) {
+        this.fileReader = fileReader;
+    }
+
+    public FileReader getFileReader() {
+        return fileReader;
+    }
+
+    public void setFtpReader(FtpReader ftpReader) {
+        this.ftpReader = ftpReader;
+    }
+
+    public FtpReader getFtpReader() {
+        return ftpReader;
+    }
+
+}

spring-core/src/main/java/com/baeldung/beaninjection/ReaderService.java

@@ -0,0 +1,14 @@
+package com.baeldung.beaninjection;
+
+public class ReaderService {
+    private FtpReader ftpReader;
+
+    public void setFtpReader(FtpReader reader) {
+        this.ftpReader = reader;
+    }
+
+    public FtpReader getFtpReader() {
+        return ftpReader;
+    }
+
+}

spring-core/src/main/resources/injectiontypes.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns="http://www.springframework.org/schema/beans"
+	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
+
+	<bean name="ftpReader" class="com.baeldung.beaninjection.FtpReader">
+		<constructor-arg value="localhost" />
+		<constructor-arg value="21" />
+	</bean>
+	
+	<bean name="readerService" class="com.baeldung.beaninjection.ReaderService">
+		<property name="ftpReader" ref="ftpReader" />
+	</bean>
+	
+</beans>

spring-core/src/test/java/com/baeldung/beaninjection/FileReaderTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.beaninjection;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = ReaderApplicationConfig.class)
+public class FileReaderTest {
+
+    @Autowired
+    private ApplicationContext context;
+
+    @Test
+    public void testAutowiredAnnotation_WhenField_ThenInjected() {
+        FileReader service = context.getBean(FileReader.class);
+        assertNotNull(service.getLocation());
+    }
+}

spring-core/src/test/java/com/baeldung/beaninjection/FtpReaderTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.beaninjection;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(locations = "classpath:injectiontypes.xml")
+public class FtpReaderTest {
+
+    @Autowired
+    private ApplicationContext context;
+
+    @Test
+    public void testXMLBeanConfig_WhenConstructorArguments_ThenInjected() {
+        FtpReader service = context.getBean(FtpReader.class);
+        assertNotNull(service.getFtpHost());
+        assertNotNull(service.getFtpPort());
+    }
+}

spring-core/src/test/java/com/baeldung/beaninjection/ReaderManagerTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.beaninjection;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = ReaderApplicationConfig.class)
+public class ReaderManagerTest {
+
+    @Autowired
+    private ApplicationContext context;
+
+    @Test
+    public void testAutowiredAnnotation_WhenConstructorAndSetter_ThenInjected() {
+        ReaderManager service = context.getBean(ReaderManager.class);
+        assertNotNull(service.getFtpReader());
+        assertNotNull(service.getFileReader());
+    }
+}

spring-core/src/test/java/com/baeldung/beaninjection/ReaderServiceTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.beaninjection;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(locations = "classpath:injectiontypes.xml")
+public class ReaderServiceTest {
+
+    @Autowired
+    private ApplicationContext context;
+
+    @Test
+    public void testXMLBeanConfig_WhenSetter_ThenInjected() {
+        ReaderService service = context.getBean(ReaderService.class);
+        assertNotNull(service.getFtpReader());
+    }
+}