diff --git a/core-java-modules/core-java-lang-oop-types/pom.xml b/core-java-modules/core-java-lang-oop-types/pom.xml
index ee167bbae2..c4efd9b8d2 100644
--- a/core-java-modules/core-java-lang-oop-types/pom.xml
+++ b/core-java-modules/core-java-lang-oop-types/pom.xml
@@ -12,12 +12,20 @@
     <artifactId>core-java-lang-oop-types</artifactId>
     <name>core-java-lang-oop-types</name>
     <packaging>jar</packaging>
-    
+
     <dependencies>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>${commons-codec.version}</version>
+        </dependency>
     </dependencies>
+    <properties>
+        <commons-codec.version>1.15</commons-codec.version>
+    </properties>
 </project>
\ No newline at end of file
diff --git a/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/Application.java b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/Application.java
new file mode 100644
index 0000000000..ad3d861d6a
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/Application.java
@@ -0,0 +1,35 @@
+package com.baeldung.enums.extendenum;
+
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.Map;
+
+public class Application {
+    private static final Map<ImmutableOperation, Operator> OPERATION_MAP;
+
+    static {
+        OPERATION_MAP = new EnumMap<>(ImmutableOperation.class);
+        OPERATION_MAP.put(ImmutableOperation.TO_LOWER, String::toLowerCase);
+        OPERATION_MAP.put(ImmutableOperation.INVERT_CASE, StringUtils::swapCase);
+        OPERATION_MAP.put(ImmutableOperation.REMOVE_WHITESPACES, input -> input.replaceAll("\\s", ""));
+
+        if (Arrays.stream(ImmutableOperation.values()).anyMatch(it -> !OPERATION_MAP.containsKey(it))) {
+            throw new IllegalStateException("Unmapped enum constant found!");
+        }
+    }
+
+    public String applyImmutableOperation(ImmutableOperation operation, String input) {
+        return OPERATION_MAP.get(operation).apply(input);
+    }
+
+    public String getDescription(StringOperation stringOperation) {
+        return stringOperation.getDescription();
+    }
+
+    public String applyOperation(StringOperation operation, String input) {
+        return operation.apply(input);
+    }
+
+}
diff --git a/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ApplicationWithEx.java b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ApplicationWithEx.java
new file mode 100644
index 0000000000..e9cbad6b7c
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ApplicationWithEx.java
@@ -0,0 +1,26 @@
+package com.baeldung.enums.extendenum;
+
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.Map;
+
+public class ApplicationWithEx {
+    private static final Map<ImmutableOperation, Operator> OPERATION_MAP;
+
+    static {
+        OPERATION_MAP = new EnumMap<>(ImmutableOperation.class);
+        OPERATION_MAP.put(ImmutableOperation.TO_LOWER, String::toLowerCase);
+        OPERATION_MAP.put(ImmutableOperation.INVERT_CASE, StringUtils::swapCase);
+        // ImmutableOperation.REMOVE_WHITESPACES is not mapped
+
+        if (Arrays.stream(ImmutableOperation.values()).anyMatch(it -> !OPERATION_MAP.containsKey(it))) {
+            throw new IllegalStateException("Unmapped enum constant found!");
+        }
+    }
+
+    public String applyImmutableOperation(ImmutableOperation operation, String input) {
+        return OPERATION_MAP.get(operation).apply(input);
+    }
+}
diff --git a/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/BasicStringOperation.java b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/BasicStringOperation.java
new file mode 100644
index 0000000000..267b02daf4
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/BasicStringOperation.java
@@ -0,0 +1,33 @@
+package com.baeldung.enums.extendenum;
+
+public enum BasicStringOperation implements StringOperation {
+    TRIM("Removing leading and trailing spaces.") {
+        @Override
+        public String apply(String input) {
+            return input.trim();
+        }
+    },
+    TO_UPPER("Changing all characters into upper case.") {
+        @Override
+        public String apply(String input) {
+            return input.toUpperCase();
+        }
+    },
+    REVERSE("Reversing the given string.") {
+        @Override
+        public String apply(String input) {
+            return new StringBuilder(input).reverse().toString();
+        }
+    };
+
+    private String description;
+
+    public String getDescription() {
+        return description;
+    }
+
+    BasicStringOperation(String description) {
+        this.description = description;
+    }
+}
+
diff --git a/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ExtendedStringOperation.java b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ExtendedStringOperation.java
new file mode 100644
index 0000000000..6184837b26
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ExtendedStringOperation.java
@@ -0,0 +1,31 @@
+package com.baeldung.enums.extendenum;
+
+import org.apache.commons.codec.binary.Base64;
+import org.apache.commons.codec.digest.DigestUtils;
+
+public enum ExtendedStringOperation implements StringOperation {
+    MD5_ENCODE("Encoding the given string using the MD5 algorithm.") {
+        @Override
+        public String apply(String input) {
+            return DigestUtils.md5Hex(input);
+        }
+    },
+    BASE64_ENCODE("Encoding the given string using the BASE64 algorithm.") {
+        @Override
+        public String apply(String input) {
+            return new String(new Base64().encode(input.getBytes()));
+        }
+    };
+
+    private String description;
+
+    ExtendedStringOperation(String description) {
+        this.description = description;
+    }
+
+
+    @Override
+    public String getDescription() {
+        return description;
+    }
+}
\ No newline at end of file
diff --git a/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ImmutableOperation.java b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ImmutableOperation.java
new file mode 100644
index 0000000000..66f26a4806
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ImmutableOperation.java
@@ -0,0 +1,6 @@
+package com.baeldung.enums.extendenum;
+
+public enum ImmutableOperation {
+    REMOVE_WHITESPACES, TO_LOWER, INVERT_CASE
+}
+
diff --git a/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/Operator.java b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/Operator.java
new file mode 100644
index 0000000000..a65fea4f92
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/Operator.java
@@ -0,0 +1,5 @@
+package com.baeldung.enums.extendenum;
+
+public interface Operator {
+    String apply(String input);
+}
diff --git a/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/StringOperation.java b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/StringOperation.java
new file mode 100644
index 0000000000..faf4f38274
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/StringOperation.java
@@ -0,0 +1,7 @@
+package com.baeldung.enums.extendenum;
+
+public interface StringOperation {
+    String getDescription();
+
+    String apply(String input);
+}
diff --git a/core-java-modules/core-java-lang-oop-types/src/test/java/com/baeldung/enums/extendenum/ExtendEnumUnitTest.java b/core-java-modules/core-java-lang-oop-types/src/test/java/com/baeldung/enums/extendenum/ExtendEnumUnitTest.java
new file mode 100644
index 0000000000..0b5ed1e826
--- /dev/null
+++ b/core-java-modules/core-java-lang-oop-types/src/test/java/com/baeldung/enums/extendenum/ExtendEnumUnitTest.java
@@ -0,0 +1,43 @@
+package com.baeldung.enums.extendenum;
+
+import org.junit.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class ExtendEnumUnitTest {
+    private Application app = new Application();
+
+    @Test
+    public void givenAStringAndOperation_whenApplyOperation_thenGetExpectedResult() {
+        String input = " hello";
+        String expectedToUpper = " HELLO";
+        String expectedReverse = "olleh ";
+        String expectedTrim = "hello";
+        String expectedBase64 = "IGhlbGxv";
+        String expectedMd5 = "292a5af68d31c10e31ad449bd8f51263";
+        assertEquals(expectedTrim, app.applyOperation(BasicStringOperation.TRIM, input));
+        assertEquals(expectedToUpper, app.applyOperation(BasicStringOperation.TO_UPPER, input));
+        assertEquals(expectedReverse, app.applyOperation(BasicStringOperation.REVERSE, input));
+        assertEquals(expectedBase64, app.applyOperation(ExtendedStringOperation.BASE64_ENCODE, input));
+        assertEquals(expectedMd5, app.applyOperation(ExtendedStringOperation.MD5_ENCODE, input));
+    }
+
+    @Test
+    public void givenAStringAndImmutableOperation_whenApplyOperation_thenGetExpectedResult() {
+        String input = " He ll O ";
+        String expectedToLower = " he ll o ";
+        String expectedRmWhitespace = "HellO";
+        String expectedInvertCase = " hE LL o ";
+        assertEquals(expectedToLower, app.applyImmutableOperation(ImmutableOperation.TO_LOWER, input));
+        assertEquals(expectedRmWhitespace, app.applyImmutableOperation(ImmutableOperation.REMOVE_WHITESPACES, input));
+        assertEquals(expectedInvertCase, app.applyImmutableOperation(ImmutableOperation.INVERT_CASE, input));
+    }
+
+    @Test
+    public void givenUnmappedImmutableOperationValue_whenAppStarts_thenGetException() {
+        Throwable throwable = assertThrows(ExceptionInInitializerError.class, () -> {
+            ApplicationWithEx appEx = new ApplicationWithEx();
+        });
+        assertTrue(throwable.getCause() instanceof IllegalStateException);
+    }
+}
\ No newline at end of file