From 20aef54e0968c98ef2dc6b817db61a7a8f51b36f Mon Sep 17 00:00:00 2001
From: sq <19shuqi@gmail.com>
Date: Wed, 5 Jul 2017 00:37:52 +0800
Subject: [PATCH 1/2] add polymorphic isMutating()

---
 src/seedu/addressbook/commands/AddCommand.java       | 5 +++++
 src/seedu/addressbook/commands/ClearCommand.java     | 5 +++++
 src/seedu/addressbook/commands/Command.java          | 2 ++
 src/seedu/addressbook/commands/DeleteCommand.java    | 6 ++++++
 src/seedu/addressbook/commands/ExitCommand.java      | 5 +++++
 src/seedu/addressbook/commands/FindCommand.java      | 5 +++++
 src/seedu/addressbook/commands/HelpCommand.java      | 5 +++++
 src/seedu/addressbook/commands/IncorrectCommand.java | 5 +++++
 src/seedu/addressbook/commands/ListCommand.java      | 6 ++++++
 src/seedu/addressbook/commands/ViewAllCommand.java   | 6 ++++++
 src/seedu/addressbook/commands/ViewCommand.java      | 7 +++++++
 src/seedu/addressbook/logic/Logic.java               | 4 +++-
 12 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/src/seedu/addressbook/commands/AddCommand.java b/src/seedu/addressbook/commands/AddCommand.java
index b0f202d42..575db3fbe 100644
--- a/src/seedu/addressbook/commands/AddCommand.java
+++ b/src/seedu/addressbook/commands/AddCommand.java
@@ -67,4 +67,9 @@ public CommandResult execute() {
         }
     }
 
+	@Override
+	public boolean isMutating() {
+	    return true;
+	}
+
 }
diff --git a/src/seedu/addressbook/commands/ClearCommand.java b/src/seedu/addressbook/commands/ClearCommand.java
index 330146aaa..877c0ed2e 100644
--- a/src/seedu/addressbook/commands/ClearCommand.java
+++ b/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;
+	}
 }
diff --git a/src/seedu/addressbook/commands/Command.java b/src/seedu/addressbook/commands/Command.java
index ccd4fcbf4..ded80039a 100644
--- a/src/seedu/addressbook/commands/Command.java
+++ b/src/seedu/addressbook/commands/Command.java
@@ -40,6 +40,8 @@ public static String getMessageForPersonListShownSummary(List<? extends ReadOnly
      * Executes the command and returns the result.
      */
     public abstract CommandResult execute();
+    
+    public abstract boolean isMutating();
 
     /**
      * Supplies the data the command will operate on.
diff --git a/src/seedu/addressbook/commands/DeleteCommand.java b/src/seedu/addressbook/commands/DeleteCommand.java
index 1dd78f85e..dcfcf20f8 100644
--- a/src/seedu/addressbook/commands/DeleteCommand.java
+++ b/src/seedu/addressbook/commands/DeleteCommand.java
@@ -39,4 +39,10 @@ public CommandResult execute() {
         }
     }
 
+
+	@Override
+	public boolean isMutating() {
+		return true;
+	}
+
 }
diff --git a/src/seedu/addressbook/commands/ExitCommand.java b/src/seedu/addressbook/commands/ExitCommand.java
index 0585451f1..463693742 100644
--- a/src/seedu/addressbook/commands/ExitCommand.java
+++ b/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;
+	}
+
 }
diff --git a/src/seedu/addressbook/commands/FindCommand.java b/src/seedu/addressbook/commands/FindCommand.java
index c8e9a380f..930aec625 100644
--- a/src/seedu/addressbook/commands/FindCommand.java
+++ b/src/seedu/addressbook/commands/FindCommand.java
@@ -53,4 +53,9 @@ private List<ReadOnlyPerson> getPersonsWithNameContainingAnyKeyword(Set<String>
         return matchedPersons;
     }
 
+	@Override
+	public boolean isMutating() {
+		return false;
+	}
+
 }
diff --git a/src/seedu/addressbook/commands/HelpCommand.java b/src/seedu/addressbook/commands/HelpCommand.java
index ef2ed7d0e..0c5aa535b 100644
--- a/src/seedu/addressbook/commands/HelpCommand.java
+++ b/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;
+	}
 }
diff --git a/src/seedu/addressbook/commands/IncorrectCommand.java b/src/seedu/addressbook/commands/IncorrectCommand.java
index 81abba7a1..69324f491 100644
--- a/src/seedu/addressbook/commands/IncorrectCommand.java
+++ b/src/seedu/addressbook/commands/IncorrectCommand.java
@@ -17,4 +17,9 @@ public CommandResult execute() {
         return new CommandResult(feedbackToUser);
     }
 
+	@Override
+	public boolean isMutating() {
+	    return false;
+	}
+
 }
diff --git a/src/seedu/addressbook/commands/ListCommand.java b/src/seedu/addressbook/commands/ListCommand.java
index cb604a8e9..b6ffacb9c 100644
--- a/src/seedu/addressbook/commands/ListCommand.java
+++ b/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;
+	}
 }
diff --git a/src/seedu/addressbook/commands/ViewAllCommand.java b/src/seedu/addressbook/commands/ViewAllCommand.java
index ed2c16e83..3e75e7944 100644
--- a/src/seedu/addressbook/commands/ViewAllCommand.java
+++ b/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;
+	}
 }
diff --git a/src/seedu/addressbook/commands/ViewCommand.java b/src/seedu/addressbook/commands/ViewCommand.java
index 1058c4b52..c8e6ff96e 100644
--- a/src/seedu/addressbook/commands/ViewCommand.java
+++ b/src/seedu/addressbook/commands/ViewCommand.java
@@ -38,4 +38,11 @@ public CommandResult execute() {
         }
     }
 
+
+	@Override
+	public boolean isMutating() {
+	    return false;
+	}
+    
+
 }
diff --git a/src/seedu/addressbook/logic/Logic.java b/src/seedu/addressbook/logic/Logic.java
index 17afd61a0..fe2bd529d 100644
--- a/src/seedu/addressbook/logic/Logic.java
+++ b/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;
     }
 

From 9b7686051ac18aaeeb25761488df1eee3aef3cd9 Mon Sep 17 00:00:00 2001
From: sq <19shuqi@gmail.com>
Date: Wed, 5 Jul 2017 15:22:25 +0800
Subject: [PATCH 2/2] Follow LSP

---
 src/seedu/addressbook/commands/AddCommand.java | 3 ++-
 src/seedu/addressbook/commands/Command.java    | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/seedu/addressbook/commands/AddCommand.java b/src/seedu/addressbook/commands/AddCommand.java
index 575db3fbe..6344a7d04 100644
--- a/src/seedu/addressbook/commands/AddCommand.java
+++ b/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));
diff --git a/src/seedu/addressbook/commands/Command.java b/src/seedu/addressbook/commands/Command.java
index ded80039a..d30274c19 100644
--- a/src/seedu/addressbook/commands/Command.java
+++ b/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 +39,9 @@ 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();