[T5A1][T01-T3] Teo Shu Qi

src/seedu/addressbook/commands/AddCommand.java

@@ -2,6 +2,7 @@
 
 import seedu.addressbook.data.exception.IllegalValueException;
 import seedu.addressbook.data.person.*;
+import seedu.addressbook.data.person.UniquePersonList.DuplicatePersonException;
 import seedu.addressbook.data.tag.Tag;
 import seedu.addressbook.data.tag.UniqueTagList;
 
@@ -58,7 +59,7 @@ public ReadOnlyPerson getPerson() {
     }
 
     @Override
-    public CommandResult execute() {
+    public CommandResult execute() throws DuplicatePersonException{
         try {
             addressBook.addPerson(toAdd);
             return new CommandResult(String.format(MESSAGE_SUCCESS, toAdd));
@@ -67,4 +68,9 @@ public CommandResult execute() {
         }
     }
 
+	@Override
+	public boolean isMutating() {
+	    return true;
+	}
+
 }

src/seedu/addressbook/commands/ClearCommand.java

@@ -16,4 +16,9 @@ public CommandResult execute() {
         addressBook.clear();
         return new CommandResult(MESSAGE_SUCCESS);
     }
+
+	@Override
+	public boolean isMutating() {
+		return true;
+	}
 }

src/seedu/addressbook/commands/Command.java

@@ -3,6 +3,7 @@
 import seedu.addressbook.common.Messages;
 import seedu.addressbook.data.AddressBook;
 import seedu.addressbook.data.person.ReadOnlyPerson;
+import seedu.addressbook.data.person.UniquePersonList.DuplicatePersonException;
 
 import java.util.List;
 
@@ -38,8 +39,11 @@ public static String getMessageForPersonListShownSummary(List<? extends ReadOnly
 
     /**
      * Executes the command and returns the result.
+     * @throws DuplicatePersonException 
      */
-    public abstract CommandResult execute();
+    public abstract CommandResult execute() throws DuplicatePersonException;
+
+    public abstract boolean isMutating();
 
     /**
      * Supplies the data the command will operate on.

src/seedu/addressbook/commands/DeleteCommand.java

@@ -39,4 +39,10 @@ public CommandResult execute() {
         }
     }
 
+
+	@Override
+	public boolean isMutating() {
+		return true;
+	}
+
 }

src/seedu/addressbook/commands/ExitCommand.java

@@ -16,4 +16,9 @@ public CommandResult execute() {
         return new CommandResult(MESSAGE_EXIT_ACKNOWEDGEMENT);
     }
 
+	@Override
+	public boolean isMutating() {
+		return false;
+	}
+
 }

src/seedu/addressbook/commands/FindCommand.java

@@ -53,4 +53,9 @@ private List<ReadOnlyPerson> getPersonsWithNameContainingAnyKeyword(Set<String>
         return matchedPersons;
     }
 
+	@Override
+	public boolean isMutating() {
+		return false;
+	}
+
 }

src/seedu/addressbook/commands/HelpCommand.java

@@ -25,4 +25,9 @@ public class HelpCommand extends Command {
     public CommandResult execute() {
         return new CommandResult(MESSAGE_ALL_USAGES);
     }
+
+	@Override
+	public boolean isMutating() {
+		return false;
+	}
 }

src/seedu/addressbook/commands/IncorrectCommand.java

@@ -17,4 +17,9 @@ public CommandResult execute() {
         return new CommandResult(feedbackToUser);
     }
 
+	@Override
+	public boolean isMutating() {
+	    return false;
+	}
+
 }

src/seedu/addressbook/commands/ListCommand.java

@@ -22,4 +22,10 @@ public CommandResult execute() {
         List<ReadOnlyPerson> allPersons = addressBook.getAllPersons().immutableListView();
         return new CommandResult(getMessageForPersonListShownSummary(allPersons), allPersons);
     }
+
+
+	@Override
+	public boolean isMutating() {
+	    return false;
+	}
 }

src/seedu/addressbook/commands/ViewAllCommand.java

@@ -37,4 +37,10 @@ public CommandResult execute() {
             return new CommandResult(Messages.MESSAGE_INVALID_PERSON_DISPLAYED_INDEX);
         }
     }
+
+
+	@Override
+	public boolean isMutating() {
+	    return false;
+	}
 }

src/seedu/addressbook/commands/ViewCommand.java

@@ -38,4 +38,11 @@ public CommandResult execute() {
         }
     }
 
+
+	@Override
+	public boolean isMutating() {
+	    return false;
+	}
+
+
 }

src/seedu/addressbook/logic/Logic.java

@@ -85,7 +85,9 @@ public CommandResult execute(String userCommandText) throws Exception {
     private CommandResult execute(Command command) throws Exception {
         command.setData(addressBook, lastShownList);
         CommandResult result = command.execute();
-        storage.save(addressBook);
+        if (command.isMutating()) {
+            storage.save(addressBook);
+        }
         return result;
     }