diff --git a/src/main/java/billgates/use_cases/delete_entry/DeleteEntryController.java b/src/main/java/billgates/use_cases/delete_entry/DeleteEntryController.java
index c527bb5..b848c4e 100644
--- a/src/main/java/billgates/use_cases/delete_entry/DeleteEntryController.java
+++ b/src/main/java/billgates/use_cases/delete_entry/DeleteEntryController.java
@@ -2,9 +2,14 @@
 
 /**
  * Clean Architecture Layer: Interface Adapters
+ * This class serves as the controller of the Delete Entry Use Case.
+ * It is only responsible for accepting the input (<code> entryID </code>) from the user and
+ * invoke the corresponding use case.
  *
  * @author Ellen, Scott
+ * @see DeleteEntryInputPort
  */
+
 public class DeleteEntryController {
 
     private final DeleteEntryInputPort useCase;
diff --git a/src/main/java/billgates/use_cases/delete_entry/DeleteEntryInputPort.java b/src/main/java/billgates/use_cases/delete_entry/DeleteEntryInputPort.java
index ffb8a3a..f9869bd 100644
--- a/src/main/java/billgates/use_cases/delete_entry/DeleteEntryInputPort.java
+++ b/src/main/java/billgates/use_cases/delete_entry/DeleteEntryInputPort.java
@@ -2,9 +2,17 @@
 
 /**
  * Clean Architecture Layer: Application Business Rules
+ * An input port for the Delete Entry use case.
  *
  * @author Ellen, Scott
+ *
+ * @see DeleteEntryUseCase
  */
 public interface DeleteEntryInputPort {
+    /**
+     * This method will delete the entry with corresponding entryID in the database.
+     *
+     * @param entryId the entryId that need to be deleted.
+     */
     void deleteEntry(int entryId);
 }
diff --git a/src/main/java/billgates/use_cases/delete_entry/DeleteEntryUseCase.java b/src/main/java/billgates/use_cases/delete_entry/DeleteEntryUseCase.java
index c27fd8f..a25c787 100644
--- a/src/main/java/billgates/use_cases/delete_entry/DeleteEntryUseCase.java
+++ b/src/main/java/billgates/use_cases/delete_entry/DeleteEntryUseCase.java
@@ -6,10 +6,17 @@
 /**
  * Clean Architecture Layer: Application Business Rules
  *
+ * A concrete implementation of the <code>DeleteEntryUseCase</code>.
+ *
  * @author Ellen, Scott
+ *
+ * @see DeleteEntryInputPort
  */
-public class DeleteEntryUseCase implements DeleteEntryInputPort {
 
+public class DeleteEntryUseCase implements DeleteEntryInputPort {
+    /**
+     * The database gateway for input/output with the database.
+     */
     private final DatabaseGateway gateway;
 
     public DeleteEntryUseCase(DatabaseGateway gateway) {