Add AbstractFindCommand

Temporary so the code does not break

src/main/java/seedu/address/logic/commands/AbstractFindCommand.java

@@ -0,0 +1,58 @@
+package seedu.address.logic.commands;
+
+import static java.util.Objects.requireNonNull;
+
+import seedu.address.commons.util.ToStringBuilder;
+import seedu.address.logic.Messages;
+import seedu.address.model.Model;
+import seedu.address.model.person.ContainsKeywordsPredicate;
+
+/**
+ * Finds and lists all persons in address book whose name contains any of the argument keywords.
+ * Keyword matching is case-insensitive.
+ */
+abstract public class AbstractFindCommand extends Command {
+
+    public static final String COMMAND_WORD = "find";
+
+    public static final String MESSAGE_USAGE = COMMAND_WORD + ": Finds all persons whose names, contacts or emails "
+            + "contain any of the specified keywords (case-insensitive) and displays them as a list with indices.\n"
+            + "Parameters: KEYWORD [MORE_KEYWORDS]...\n"
+            + "Example: " + COMMAND_WORD + " alice bob charlie";
+
+    private final ContainsKeywordsPredicate predicate;
+
+    public AbstractFindCommand(ContainsKeywordsPredicate predicate) {
+        this.predicate = predicate;
+    }
+
+    @Override
+    public CommandResult execute(Model model) {
+        requireNonNull(model);
+        model.updateFilteredPersonList(this.predicate);
+        return new CommandResult(
+                String.format(Messages.MESSAGE_PERSONS_LISTED_OVERVIEW, model.getFilteredPersonList().size()));
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this) {
+            return true;
+        }
+
+        // instanceof handles nulls
+        if (!(other instanceof AbstractFindCommand)) {
+            return false;
+        }
+
+        AbstractFindCommand otherFindCommand = (AbstractFindCommand) other;
+        return this.predicate.equals(otherFindCommand.predicate);
+    }
+
+    @Override
+    public String toString() {
+        return new ToStringBuilder(this)
+                .add("predicate", this.predicate)
+                .toString();
+    }
+}

src/main/java/seedu/address/logic/commands/FindCommand.java

@@ -9,9 +9,9 @@
 
 /**
  * Finds and lists all persons in address book whose name contains any of the argument keywords.
- * Keyword matching is case insensitive.
+ * Keyword matching is case-insensitive.
  */
-abstract public class FindCommand extends Command {
+public class FindCommand extends Command {
 
     public static final String COMMAND_WORD = "find";