Detect duplicate tasks

lite.txt

@@ -1,4 +1,3 @@
 D!0!return book!by 2020-10-15 18:30
 E!0!project meeting!from 2020-08-10 15:30!to 2020-08-10 17:30
 T!0!read a book
-T!0!do a test

src/main/java/lite/Ui.java

@@ -58,7 +58,7 @@ public String deleteTask(String instruction[], TaskList tasks) {
             tasks.remove(index);
             assert tasks.size() == size - 1 : "size of array decreased by 1";
             return output;
-        } catch (NullPointerException | ArrayIndexOutOfBoundsException e){
+        } catch (NullPointerException | IndexOutOfBoundsException e){
             return LiteException.deleteException(tasks);
         }
     }
@@ -73,10 +73,13 @@ public String addToDoTask(String instruction[], TaskList tasks) {
             String description = instruction[1];
             Task todo = new Todo(description);
             int size = tasks.size();
-            tasks.add(todo);
+            boolean isDuplicate = tasks.add(todo);
+            if (isDuplicate) {
+                return Printer.printDuplicateFound();
+            }
             assert tasks.size() == size + 1 : "size of array increased by 1";
             return Printer.printTask(tasks, todo);
-        } catch (ArrayIndexOutOfBoundsException e) {
+        } catch (IndexOutOfBoundsException e) {
             return LiteException.toDoException();
         }
     }
@@ -93,10 +96,13 @@ public String addDeadlineTask(String instruction[], TaskList tasks) {
             String due = splits[1];
             Task deadline = new Deadline(description, due);
             int size = tasks.size();
-            tasks.add(deadline);
+            boolean isDuplicate = tasks.add(deadline);
+            if (isDuplicate) {
+                return Printer.printDuplicateFound();
+            }
             assert tasks.size() == size + 1 : "size of array increased by 1";
             return Printer.printTask(tasks, deadline);
-        } catch (ArrayIndexOutOfBoundsException e) {
+        } catch (IndexOutOfBoundsException e) {
             return LiteException.deadlineException();
         }
     }
@@ -114,10 +120,13 @@ public String addEventTask(String[] instruction, TaskList tasks) {
             String end = splits[2];
             Task event = new Event(description, start, end);
             int size = tasks.size();
-            tasks.add(event);
+            boolean isDuplicate = tasks.add(event);
+            if (isDuplicate) {
+                return Printer.printDuplicateFound();
+            }
             assert tasks.size() == size + 1 : "size of array increased by 1";
             return Printer.printTask(tasks, event);
-        } catch (ArrayIndexOutOfBoundsException e) {
+        } catch (IndexOutOfBoundsException e) {
             return LiteException.eventException();
         }
     }

src/main/java/lite/task/Task.java

@@ -76,4 +76,12 @@ public String saveToFile() {
         return (this.isDone ? "1" : "0")
                 + "!" + this.description;
     }
+
+    @Override
+    public boolean equals (Object obj) {
+        Task task = (Task) obj;
+        System.out.println(this.toString());
+        System.out.println(task.toString());
+        return this.toString().equals(task.toString());
+    }
 }

src/main/java/lite/task/TaskList.java

@@ -4,6 +4,8 @@
 import lite.util.Printer;
 
 import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.Set;
 
 public class TaskList {
     private ArrayList<Task> tasks;
@@ -44,8 +46,12 @@ public Task get(int i) {
      * Adds a task to the array list
      * @param task Task to be added
      */
-    public void add (Task task) {
+    public boolean add (Task task) {
+        if (tasks.contains(task)) {
+            return true;
+        }
         this.tasks.add(task);
+        return false;
     }
 
     /**

src/main/java/lite/util/Printer.java

@@ -53,4 +53,8 @@ public static String printFound(TaskList tasks) {
     public static String printNotFound() {
         return "There are no tasks that correspond with your input";
     }
+
+    public static String printDuplicateFound() {
+        return "This task is already in your Task List.";
+    }
 }