Merge branch 'branch-Level-9' into master

src/main/java/duke/Parser.java

@@ -1,12 +1,6 @@
 package duke;
 
-import duke.command.AddCommand;
-import duke.command.Command;
-import duke.command.DeleteCommand;
-import duke.command.DoneCommand;
-import duke.command.DueCommand;
-import duke.command.ExitCommand;
-import duke.command.ListCommand;
+import duke.command.*;
 import duke.task.TaskType;
 
 import java.time.LocalDate;
@@ -134,6 +128,8 @@ public static Command parse(String fullCommand) throws DukeException {
             }
 
             return new DeleteCommand(Integer.parseInt(args));
+        case "find":
+            return new FindCommand(args);
         case "todo":
             return new AddCommand(TaskType.TODO, args);
         case "deadline": {

src/main/java/duke/TaskList.java

@@ -95,6 +95,10 @@ public List<Task> getDueTasks(LocalDate date) {
         return tasks.stream().filter(task -> task.isDue(date)).collect(Collectors.toList());
     }
 
+    public List<Task> findTasks(String keyword) {
+        return tasks.stream().filter(task -> task.hasKeyword(keyword)).collect(Collectors.toList());
+    }
+
     public List<Task> getTasks() {
         return tasks;
     }

src/main/java/duke/command/FindCommand.java

@@ -0,0 +1,36 @@
+package duke.command;
+
+import duke.DukeException;
+import duke.Storage;
+import duke.TaskList;
+import duke.Ui;
+import duke.task.Task;
+
+import java.time.format.DateTimeFormatter;
+import java.util.List;
+
+public class FindCommand extends Command {
+    private final String keyword;
+
+    public FindCommand(String keyword) {
+        this.keyword = keyword;
+    }
+
+    @Override
+    public void execute(TaskList tasks, Ui ui, Storage storage) throws DukeException {
+        List<Task> foundTasks = tasks.findTasks(keyword);
+
+        if (foundTasks.size() == 0) {
+            throw new DukeException("There are no tasks in your list with the keyword \""
+                    + keyword + "\".");
+        }
+
+        StringBuilder output = new StringBuilder("Here are the matching tasks in your list:\n");
+
+        for (Task task : foundTasks) {
+            output.append(tasks.getTasks().indexOf(task) + 1).append(".").append(task).append('\n');
+        }
+
+        ui.showPrompt(output.toString());
+    }
+}

src/main/java/duke/task/Task.java

@@ -22,6 +22,10 @@ public Task(String description, boolean isDone) {
      */
     public abstract boolean isDue(LocalDate date);
 
+    public boolean hasKeyword(String keyword) {
+        return description.contains(keyword);
+    }
+
     /**
      * Returns a status icon corresponding to whether the task is done.
      *