Sort command logic

src/seedu/addressbook/commands/Command.java

@@ -41,7 +41,7 @@ public static String getMessageForPersonListShownSummary(List<? extends ReadOnly
      */
     public CommandResult execute(){
         throw new UnsupportedOperationException("This method is to be implemented by child classes");
-    };
+    }
 
     /**
      * Supplies the data the command will operate on.

src/seedu/addressbook/commands/SortCommand.java

@@ -0,0 +1,29 @@
+package seedu.addressbook.commands;
+
+import seedu.addressbook.data.person.ReadOnlyPerson;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+public class SortCommand extends Command{
+    public static final String COMMAND_WORD = "sort";
+
+    public static final String MESSAGE_USAGE = COMMAND_WORD
+        + ": Displays all persons in the address book as a list sorted by name with index numbers.\n"
+        + "Example: " + COMMAND_WORD;
+
+    class SortByName implements Comparator<ReadOnlyPerson> {
+        public int compare (ReadOnlyPerson person1, ReadOnlyPerson person2) {
+            return person1.getName().toString().compareTo(person2.getName().toString());
+        }
+    }
+
+    @Override
+    public CommandResult execute() {
+        List<ReadOnlyPerson> allPersons = addressBook.getAllPersons().immutableListView();
+        Collections.sort(allPersons, new SortByName());
+        return new CommandResult(getMessageForPersonListShownSummary(allPersons), allPersons);
+    }
+}

test/java/seedu/addressbook/commands/FindCommandTest.java

@@ -1,7 +1,5 @@
 package seedu.addressbook.commands;
 
-import static org.junit.Assert.assertEquals;
-
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
@@ -15,6 +13,8 @@
 import seedu.addressbook.data.person.ReadOnlyPerson;
 import seedu.addressbook.util.TypicalPersons;
 
+import static org.testng.AssertJUnit.assertEquals;
+
 public class FindCommandTest {
 
     private final AddressBook addressBook = new TypicalPersons().getTypicalAddressBook();