[W6.4d][F09-B4]Zhong ZhengXin

src/seedu/addressbook/commands/AddCommand.java

@@ -67,4 +67,9 @@ 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

@@ -70,4 +70,10 @@ public int getTargetIndex() {
     public void setTargetIndex(int targetIndex) {
         this.targetIndex = targetIndex;
     }
+
+    public abstract boolean isMutating( );
+    /**
+     * Checks whether the commands change the data
+     */
+
 }

src/seedu/addressbook/commands/DeleteCommand.java

@@ -39,4 +39,9 @@ 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

@@ -36,6 +36,11 @@ public CommandResult execute() {
         return new CommandResult(getMessageForPersonListShownSummary(personsFound), personsFound);
     }
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
+
     /**
      * Retrieve all persons in the address book whose names contain some of the specified keywords.
      *

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 +22,9 @@ 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 +37,9 @@ 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 +38,9 @@ public CommandResult execute() {
         }
     }
 
+    @Override
+    public boolean isMutating() {
+        return false;
+    }
+
 }

src/seedu/addressbook/logic/Logic.java

@@ -76,7 +76,7 @@ public CommandResult execute(String userCommandText) throws Exception {
     }
 
     /**
-     * Executes the command, updates storage, and returns the result.
+     * Executes the command, updates storage only when the data is mutated, and returns the result.
      *
      * @param command user command
      * @return result of the command
@@ -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;
     }
 

test/java/seedu/addressbook/logic/LogicTest.java

@@ -13,6 +13,7 @@
 import seedu.addressbook.data.tag.Tag;
 import seedu.addressbook.data.tag.UniqueTagList;
 import seedu.addressbook.storage.StorageFile;
+import seedu.addressbook.parser.Parser;
 
 import java.util.*;
 
@@ -90,7 +91,10 @@ private void assertCommandBehavior(String inputCommand,
         //Confirm the state of data is as expected
         assertEquals(expectedAddressBook, addressBook);
         assertEquals(lastShownList, logic.getLastShownList());
-        assertEquals(addressBook, saveFile.load());
+        if(new Parser().parseCommand(inputCommand).isMutating()) {
+            assertEquals(addressBook, saveFile.load());
+        }
+
     }