new module has been added

java-collections-maps-3/README.md

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+## Java Collections Cookbooks and Examples
+
+This module contains articles about Map data structures in Java.
+
+### Relevant Articles: 
+- [Java Map With Case-Insensitive Keys](https://www.baeldung.com/java-map-case-insensitive-keys)
+- More articles: [[<-- prev>]](/../java-collections-maps)
+- More articles: [[<-- prev>]](/../java-collections-maps-2)

java-collections-maps-3/pom.xml

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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">
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>java-collections-maps-3</artifactId>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-core</artifactId>
+            <version>${spring.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    <dependency>
+        <groupId>org.apache.commons</groupId>
+        <artifactId>commons-collections4</artifactId>
+        <version>${commons-collections4.version}</version>
+    </dependency>
+    </dependencies>
+
+    <properties>
+        <commons-collections4.version>4.1</commons-collections4.version>
+        <assertj.version>3.6.1</assertj.version>
+        <spring.version>5.2.5.RELEASE</spring.version>
+    </properties>
+</project>

java-collections-maps-3/src/test/java/com/baeldung/map/caseinsensitivekeys/CaseInsensitiveMapUnitTest.java

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+package com.baeldung.map.caseinsensitivekeys;
+
+import org.apache.commons.collections4.map.CaseInsensitiveMap;
+import org.junit.Assert;
+import org.junit.Test;
+import org.springframework.util.LinkedCaseInsensitiveMap;
+import static org.junit.Assert.*;
+
+import java.util.TreeMap;
+
+public class CaseInsensitiveMapUnitTest {
+    @Test
+    public void givenCaseInsensitiveTreeMap_whenTwoEntriesAdded_thenSizeIsOne(){
+        TreeMap<String, Integer> treeMap = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
+        treeMap.put("abc", 1);
+        treeMap.put("ABC", 2);
+
+        assertEquals(treeMap.size(), 1);
+    }
+
+    @Test
+    public void givenCommonsCaseInsensitiveMap_whenSameEntryAdded_thenValueUpdated(){
+        CaseInsensitiveMap<String, Integer> commonsHashMap = new CaseInsensitiveMap<>();
+        commonsHashMap.put("abc", 1);
+        commonsHashMap.put("ABC", 2);
+
+        Assert.assertEquals(commonsHashMap.get("aBc"), (Integer)2);
+    }
+
+    @Test
+    public void givenLinkedCaseInsensitiveMap_whenEntryRemoved_thenSizeIsZero(){
+        LinkedCaseInsensitiveMap<Integer> linkedHashMap = new LinkedCaseInsensitiveMap<>();
+        linkedHashMap.put("abc", 3);
+        linkedHashMap.remove("aBC");
+
+        Assert.assertEquals(linkedHashMap.size(), 0);
+    }
+}