todo/src/main/java/ru/kamask/pet/TodoApp.java

@@ -8,6 +8,7 @@ public class TodoApp {
     private static Scanner scanner = new Scanner(System.in);
 
     public static void main(String[] args) {
+
         /*
          * System.out.println("\n\nDeveloper mode:\n\n");
          * 
@@ -15,6 +16,8 @@ public class TodoApp {
          * Task t2 = new Task("Дело тест - t2", "");
          * Task t3 = new Task("Дело тест - t3", "");
          * printAll(t1, t2, t3);
+         * System.out.println(markTaskCompletedById(new Task[] { t1, t2, t3 }, 2));
+         * printAll(t1, t2, t3);
          * 
          * System.out.println("\n\n" + "*".repeat(20) + "\n\n");
          */
@@ -162,4 +165,14 @@ public class TodoApp {
                 t.printInfo();
     }
 
+    private static boolean markTaskCompletedById(Task[] tasks, int id) {
+        for (Task t : tasks)
+            if (t != null && t.getId() == id) {
+                if (!t.getCompleted())
+                    t.toggleCompleted();
+                return true;
+            }
+        return false;
+    }
+
 }