Question

I have one table in sqlite database which contains five different columns as shown below.

CATEGORY    NOTE     DATE         PRICE       MODE
travel      delhi    10/5/2011    800          cash
food        daily    9/5/2011     500          cash
travel      goa       12/5/2011    1000         cash

The values in database are added by runtime from user. After all I retrieve it through content provider and store into an ArrayList and shown onto listview. But right now I want show it as per category means I want shown a category below that all its tasks then next category & its tasks like this. Item is class which contains all columnames as data members & its setter’s and getter’s. Any help will be appreciated.

Answer 1

Use Guava’s MultiMaps.index method. It will create a MultiMap, i.e. a Map with categories as keys, and the list of items as values.

If you can’t use Guava, then do what this method does:

• create a Map<String, List<Item>> where the key is the category
• iterate through the list of items, and place each item in the map

Here’s an example:

Map<String, List<Item>> itemsByCategory = new LinkedHashMap<String, List<Item>>();
for (Item item : theListOfItems) {
    String category = item.getCategory();
    List<Item> itemsOfCategory = itemsByCategory.get(category);
    if (itemsOfCategory == null) {
        itemsOfCategory = new ArrayList<Item>();
        itemsByCategory.put(category, itemsOfCategory);
    }
    itemsOfCategory.add(item);
}

for (Map.Entry<String, List<Item>> entry : itemsByCategory.entrySet()) {
    System.out.println("Category " + entry.getKey() + ":");
    for (Item item : entry.getValue()) {
        System.out.println("    Item : " + item);
    }
}