Task Not Found Exception

What should we do when a user tries to update a task that doesn't exist?

This is certainly an error case, so let's create a custom exception to model this error.

Create the Task Not Found Exception

To keep things organised we'll create a dedicated package for our exceptions, com.devtiro.task.exception.

In this new package we'll create the TaskNotFoundException:

/** Thrown when a task is not found. */
public class TaskNotFoundException extends RuntimeException {

  /** The error message template. */
  public static final String ERROR_MESSAGE =
    "Task with ID '%s' does not exist";

  /** The ID of the task that was not found. */
  private final UUID id;

  /**
   * Constructs a new TaskNotFoundException using
   * the ID of the task not found.
   *
   * @param id The ID of the task not found.
   */
  public TaskNotFoundException(UUID id) {
    super(String.format(ERROR_MESSAGE, id));
    this.id = id;
  }

  public UUID getId() {
    return id;
  }

}

This exception has a single constructor that expects the ID of the task that wasn't found. It uses this ID to create a custom error message that it passes to the superclass constructor.

This way we can capture the ID and get a helpful error message in the stack trace.

Now we can move on to the business logic.

Summary

Created the TaskNotFoundException class.