BAEL-3091: The Prototype Pattern in Java (changed code based on valid comments from a reader)

java-collections-conversions-2/README.md

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+## Java Collections Cookbooks and Examples
+
+This module contains articles about conversions among Collection types and arrays in Java.
+
+### Relevant Articles: 
+- [Array to String Conversions](https://www.baeldung.com/java-array-to-string)
+- More articles: [[<-- prev]](../java-collections-conversions)

java-collections-conversions-2/pom.xml

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+<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>java-collections-conversions-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>java-collections-conversions-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>java-collections-conversions-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+    </properties>
+</project>

java-collections-conversions-2/src/test/java/com/baeldung/convertarraytostring/ArrayToStringUnitTest.java

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+package com.baeldung.convertarraytostring;
+
+import com.google.common.base.Joiner;
+import com.google.common.base.Splitter;
+import org.apache.commons.lang3.StringUtils;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertEquals;
+
+public class ArrayToStringUnitTest {
+    
+    // convert with Java
+    
+    @Test
+    public void givenAStringArray_whenConvertBeforeJava8_thenReturnString() {
+
+        String[] strArray = { "Convert", "Array", "With", "Java" };
+        StringBuilder stringBuilder = new StringBuilder();
+        
+        for (int i = 0; i < strArray.length; i++) {
+            stringBuilder.append(strArray[i]);
+        }
+        String joinedString = stringBuilder.toString();
+        
+        assertThat(joinedString, instanceOf(String.class));
+        assertEquals("ConvertArrayWithJava", joinedString);
+    }
+
+    @Test
+    public void givenAString_whenConvertBeforeJava8_thenReturnStringArray() {
+
+        String input = "lorem ipsum dolor sit amet";
+        String[] strArray = input.split(" ");
+
+        assertThat(strArray, instanceOf(String[].class));
+        assertEquals(5, strArray.length);
+        
+        input = "loremipsum";
+        strArray = input.split("");
+        assertThat(strArray, instanceOf(String[].class));
+        assertEquals(10, strArray.length);        
+    }    
+    
+    @Test
+    public void givenAnIntArray_whenConvertBeforeJava8_thenReturnString() {
+
+        int[] strArray = { 1, 2, 3, 4, 5 };
+        StringBuilder stringBuilder = new StringBuilder();
+        
+        for (int i = 0; i < strArray.length; i++) {
+            stringBuilder.append(Integer.valueOf(strArray[i]));
+        }
+        String joinedString = stringBuilder.toString();
+        
+        assertThat(joinedString, instanceOf(String.class));
+        assertEquals("12345", joinedString);
+    }    
+    
+    // convert with Java Stream API
+    
+    @Test
+    public void givenAStringArray_whenConvertWithJavaStream_thenReturnString() {
+
+        String[] strArray = { "Convert", "With", "Java", "Streams" };
+        String joinedString = Arrays.stream(strArray)
+            .collect(Collectors.joining());
+        assertThat(joinedString, instanceOf(String.class));
+        assertEquals("ConvertWithJavaStreams", joinedString);
+        
+        joinedString = Arrays.stream(strArray)
+            .collect(Collectors.joining(","));
+        assertThat(joinedString, instanceOf(String.class));
+        assertEquals("Convert,With,Java,Streams", joinedString);
+    }    
+    
+    
+    // convert with Apache Commons
+
+    @Test
+    public void givenAStringArray_whenConvertWithApacheCommons_thenReturnString() {
+
+        String[] strArray = { "Convert", "With", "Apache", "Commons" };
+        String joinedString = StringUtils.join(strArray);
+
+        assertThat(joinedString, instanceOf(String.class));
+        assertEquals("ConvertWithApacheCommons", joinedString);
+    }
+    
+    @Test
+    public void givenAString_whenConvertWithApacheCommons_thenReturnStringArray() {
+
+        String input = "lorem ipsum dolor sit amet";
+        String[] strArray = StringUtils.split(input, " ");
+        
+        assertThat(strArray, instanceOf(String[].class));
+        assertEquals(5, strArray.length);
+    }  
+
+    
+    // convert with Guava
+
+    @Test
+    public void givenAStringArray_whenConvertWithGuava_thenReturnString() {
+
+        String[] strArray = { "Convert", "With", "Guava", null };
+        String joinedString = Joiner.on("")
+            .skipNulls()
+            .join(strArray);
+
+        assertThat(joinedString, instanceOf(String.class));
+        assertEquals("ConvertWithGuava", joinedString);
+    }
+    
+    
+    @Test
+    public void givenAString_whenConvertWithGuava_thenReturnStringArray() {
+
+        String input = "lorem ipsum dolor sit amet";
+                        
+        List<String> resultList = Splitter.on(' ')
+            .trimResults()
+            .omitEmptyStrings()
+            .splitToList(input);   
+        String[] strArray = resultList.toArray(new String[0]);
+        
+        assertThat(strArray, instanceOf(String[].class));
+        assertEquals(5, strArray.length);    
+    }  
+}