Mental Model: Todo List TUI in Java

A todo app is a tiny data system with a command shell on top.

Think Like a Data Steward

Your job is to keep task data correct over time.

  1. Load tasks from disk.
  2. Mutate tasks in memory.
  3. Persist after successful mutation.

That load-mutate-save cycle is the real app.

Task Store Mental Model

In Java, your Store class is the center.

  • List<Task> is current state.
  • nextId ensures stable IDs.
  • methods (add, markDone, remove) are controlled mutations.

If all writes go through Store, you avoid state chaos.

IDs Are Product Design

Beginners often underestimate IDs.

  • index in list is temporary
  • task ID is stable identity

When users say “done 3”, they mean ID 3, not third visible row. That one idea prevents a lot of subtle bugs.

Java-Specific Insight

Java helps model this clearly with a tiny Task type and explicit methods.

  • state transitions are visible (done = true)
  • save points are explicit (store.save())
  • error paths are obvious (task not found)

Readable beats clever every time.

Reliable Mutation Pattern

For each write command:

  1. validate input
  2. attempt mutation
  3. if mutation succeeded, save
  4. print outcome

That pattern is production thinking in beginner form.

Growth Moves

Try adding:

  • priority field
  • due date
  • sort by status

But keep the same backbone: one store, controlled mutations, explicit save.