diff --git a/java-collections-maps-3/src/main/java/com/baeldung/map/entry/Book.java b/java-collections-maps-3/src/main/java/com/baeldung/map/entry/Book.java
new file mode 100644
index 0000000000..7e47e22908
--- /dev/null
+++ b/java-collections-maps-3/src/main/java/com/baeldung/map/entry/Book.java
@@ -0,0 +1,35 @@
+package com.baeldung.map.entry;
+
+public class Book {
+    private String title;
+    private String author;
+
+    public Book(String title, String author) {
+        this.title = title;
+        this.author = author;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    public void setAuthor(String author) {
+        this.author = author;
+    }
+
+    @Override
+    public String toString() {
+        return "Book{" +
+                "title='" + title + '\'' +
+                ", author='" + author + '\'' +
+                '}';
+    }
+}
diff --git a/java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryEfficiencyExample.java b/java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryEfficiencyExample.java
new file mode 100644
index 0000000000..d64bcb38df
--- /dev/null
+++ b/java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryEfficiencyExample.java
@@ -0,0 +1,34 @@
+package com.baeldung.map.entry;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class MapEntryEfficiencyExample {
+
+    public static void main(String[] args) {
+        MapEntryEfficiencyExample mapEntryEfficiencyExample = new MapEntryEfficiencyExample();
+        Map<String, String> map = new HashMap<>();
+
+        map.put("Robert C. Martin", "Clean Code");
+        map.put("Joshua Bloch", "Effective Java");
+
+        System.out.println("Iterating Using Map.KeySet - 2 operations");
+        mapEntryEfficiencyExample.usingKeySet(map);
+
+        System.out.println("Iterating Using Map.Entry - 1 operation");
+        mapEntryEfficiencyExample.usingEntrySet(map);
+
+    }
+
+    public void usingKeySet(Map<String, String> bookMap) {
+        for (String key : bookMap.keySet()) {
+            System.out.println("key: " + key + " value: " + bookMap.get(key));
+        }
+    }
+
+    public void usingEntrySet(Map<String, String> bookMap) {
+        for (Map.Entry<String, String> book: bookMap.entrySet()) {
+            System.out.println("key: " + book.getKey() + " value: " + book.getValue());
+        }
+    }
+}
diff --git a/java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryTupleExample.java b/java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryTupleExample.java
new file mode 100644
index 0000000000..edcbd263fe
--- /dev/null
+++ b/java-collections-maps-3/src/main/java/com/baeldung/map/entry/MapEntryTupleExample.java
@@ -0,0 +1,25 @@
+package com.baeldung.map.entry;
+
+import java.util.*;
+
+public class MapEntryTupleExample {
+
+    public static void main(String[] args) {
+        Map.Entry<String, Book> tuple1;
+        Map.Entry<String, Book> tuple2;
+        Map.Entry<String, Book> tuple3;
+
+        tuple1 = new AbstractMap.SimpleEntry<>("9780134685991", new Book("Effective Java 3d Edition", "Joshua Bloch"));
+        tuple2 = new AbstractMap.SimpleEntry<>("9780132350884", new Book("Clean Code", "Robert C Martin"));
+        tuple3 = new AbstractMap.SimpleEntry<>("9780132350884", new Book("Clean Code", "Robert C Martin"));
+
+        List<Map.Entry<String, Book>> orderedTuples = new ArrayList<>();
+        orderedTuples.add(tuple1);
+        orderedTuples.add(tuple2);
+        orderedTuples.add(tuple3);
+
+        for (Map.Entry<String, Book> tuple : orderedTuples) {
+            System.out.println("key: " + tuple.getKey() + " value: " + tuple.getValue());
+        }
+    }
+}
diff --git a/java-collections-maps-3/src/test/java/com/baeldung/map/entry/MapEntryUnitTest.java b/java-collections-maps-3/src/test/java/com/baeldung/map/entry/MapEntryUnitTest.java
new file mode 100644
index 0000000000..7340558023
--- /dev/null
+++ b/java-collections-maps-3/src/test/java/com/baeldung/map/entry/MapEntryUnitTest.java
@@ -0,0 +1,33 @@
+package com.baeldung.map.entry;
+
+import org.junit.Test;
+
+import java.util.*;
+
+import static org.junit.Assert.assertEquals;
+
+public class MapEntryUnitTest {
+
+    @Test
+    public void givenSimpleEntryList_whenAddDuplicateKey_thenDoesNotOverwriteExistingKey() {
+        List<Map.Entry<String, Book>> orderedTuples = new ArrayList<>();
+        orderedTuples.add(new AbstractMap.SimpleEntry<>("9780134685991", new Book("Effective Java 3d Edition", "Joshua Bloch")));
+        orderedTuples.add(new AbstractMap.SimpleEntry<>("9780132350884", new Book("Clean Code", "Robert C Martin")));
+        orderedTuples.add(new AbstractMap.SimpleEntry<>("9780132350884", new Book("Clean Code", "Robert C Martin")));
+
+        assertEquals(3, orderedTuples.size());
+        assertEquals("9780134685991", orderedTuples.get(0).getKey());
+        assertEquals("9780132350884", orderedTuples.get(1).getKey());
+        assertEquals("9780132350884", orderedTuples.get(2).getKey());
+    }
+
+    @Test
+    public void givenRegularMap_whenAddDuplicateKey_thenOverwritesExistingKey() {
+        Map<String, Book> entries = new HashMap<>();
+        entries.put("9780134685991", new Book("Effective Java 3d Edition", "Joshua Bloch"));
+        entries.put("9780132350884", new Book("Clean Code", "Robert C Martin"));
+        entries.put("9780132350884", new Book("Clean Code", "Robert C Martin"));
+
+        assertEquals(2, entries.size());
+    }
+}