[W6.1d][W09-B1] Fan Yuting

src/seedu/addressbook/commands/AddCommand.java

@@ -57,6 +57,11 @@ public ReadOnlyPerson getPerson() {
         return toAdd;
     }
 
+    @Override
+    public boolean isMutating() {
+        return true;
+    }
+
     @Override
     public CommandResult execute() {
         try {

src/seedu/addressbook/commands/ClearCommand.java

@@ -11,6 +11,11 @@ public class ClearCommand extends Command {
 
     public static final String MESSAGE_SUCCESS = "Address book has been cleared!";
 
+    @Override
+    public boolean isMutating() {
+        return true;
+    }
+
     @Override
     public CommandResult execute() {
         addressBook.clear();

src/seedu/addressbook/commands/Command.java

@@ -26,6 +26,12 @@ public Command(int targetIndex) {
     protected Command() {
     }
 
+    /**
+     * Checks whether the command type mutates the data
+     * @return true if the data is mutated, false otherwise
+     */
+    public abstract boolean isMutating();
+
     /**
      * Constructs a feedback message to summarise an operation that displayed a listing of persons.
      *

src/seedu/addressbook/commands/DeleteCommand.java

@@ -24,6 +24,10 @@ public DeleteCommand(int targetVisibleIndex) {
         super(targetVisibleIndex);
     }
 
+    @Override
+    public boolean isMutating() {
+        return true;
+    }
 
     @Override
     public CommandResult execute() {

src/seedu/addressbook/commands/ExitCommand.java

@@ -11,6 +11,11 @@ public class ExitCommand extends Command {
             + "Example: " + COMMAND_WORD;
     public static final String MESSAGE_EXIT_ACKNOWEDGEMENT = "Exiting Address Book as requested ...";
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
+
     @Override
     public CommandResult execute() {
         return new CommandResult(MESSAGE_EXIT_ACKNOWEDGEMENT);

src/seedu/addressbook/commands/FindCommand.java

@@ -30,6 +30,11 @@ public Set<String> getKeywords() {
         return new HashSet<>(keywords);
     }
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
+
     @Override
     public CommandResult execute() {
         final List<ReadOnlyPerson> personsFound = getPersonsWithNameContainingAnyKeyword(keywords);

src/seedu/addressbook/commands/HelpCommand.java

@@ -21,6 +21,11 @@ public class HelpCommand extends Command {
             + "\n" + HelpCommand.MESSAGE_USAGE
             + "\n" + ExitCommand.MESSAGE_USAGE;
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
+
     @Override
     public CommandResult execute() {
         return new CommandResult(MESSAGE_ALL_USAGES);

src/seedu/addressbook/commands/IncorrectCommand.java

@@ -12,6 +12,11 @@ public IncorrectCommand(String feedbackToUser){
         this.feedbackToUser = feedbackToUser;
     }
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
+
     @Override
     public CommandResult execute() {
         return new CommandResult(feedbackToUser);

src/seedu/addressbook/commands/ListCommand.java

@@ -16,6 +16,10 @@ public class ListCommand extends Command {
             + "Displays all persons in the address book as a list with index numbers.\n\t"
             + "Example: " + COMMAND_WORD;
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
 
     @Override
     public CommandResult execute() {

src/seedu/addressbook/commands/ViewAllCommand.java

@@ -24,6 +24,10 @@ public ViewAllCommand(int targetVisibleIndex) {
         super(targetVisibleIndex);
     }
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
 
     @Override
     public CommandResult execute() {

src/seedu/addressbook/commands/ViewCommand.java

@@ -24,6 +24,10 @@ public ViewCommand(int targetVisibleIndex) {
         super(targetVisibleIndex);
     }
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
 
     @Override
     public CommandResult execute() {

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;
     }