java/com/google/lizlooney/shoppinglist/Categories.java

package com.google.lizlooney.shoppinglist;

import java.util.List;
import java.util.TreeSet;

/**
 * Class maintaining the set of all categories.
 *
 * @author lizlooney@gmail.com (Liz Looney)
 */
public final class Categories {
  private final Object lock = new Object();
  private final TreeSet<String> categories = new TreeSet<>();

  public void loadCategories(List<Item> items) {
    synchronized (lock) {
      // Loads the categories TreeSet with the categories that are used in the items.
      clear();
      for (Item item: items) {
        add(item);
      }
    }
  }

  public void clear() {
    synchronized (lock) {
      categories.clear();
    }
  }

  public void add(Item item) {
    synchronized (lock) {
      categories.add(item.getCategory());
    }
  }

  public String[] getCategoriesArray() {
    synchronized (lock) {
      return categories.toArray(new String[0]);
    }
  }
}