BAEL-8901 Add section in "Stream operations on Strings" article

- Added string array to map example.

java-strings/src/test/java/com/baeldung/string/JoinerSplitterUnitTest.java

@@ -3,7 +3,9 @@ package com.baeldung.string;
 import org.junit.Test;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
 
@@ -62,5 +64,20 @@ public class JoinerSplitterUnitTest {
         assertEquals(result, expectation);
 
     }
+    
+    @Test
+    public void givenStringArray_transformedToStream_convertToMap() {
+
+        String[] programming_languages = new String[] {"language:java","os:linux","editor:emacs"};
+        
+        Map<String,String> expectation=new HashMap<>();
+        expectation.put("language", "java");
+        expectation.put("os", "linux");
+        expectation.put("editor", "emacs");
+        
+        Map<String, String> result = JoinerSplitter.arrayToMap(programming_languages);
+        assertEquals(result, expectation);
+        
+    }
 
 }