Unlock the Power of NavigableMap in Java
When it comes to navigating through map entries in Java, the NavigableMap interface is the way to go. As a type of SortedMap, it offers a range of features that make it easy to traverse and manipulate map data.
What is NavigableMap?
The NavigableMap interface is a part of the Java collections framework, designed to provide efficient navigation among map entries. Since it’s an interface, you can’t create objects directly from it. Instead, you’ll need to use a class that implements NavigableMap, such as the TreeMap class.
Getting Started with NavigableMap
To use NavigableMap, you’ll need to import the java.util.NavigableMap package. Once you’ve done that, you can create a navigable map using the TreeMap class. Here’s an example:
NavigableMap<String, Integer> numbers = new TreeMap<>();
In this example, we’ve created a navigable map called numbers with string keys and integer values.
Understanding Map Components
Before we dive deeper into NavigableMap, let’s quickly review the two main components of a map:
- Key: A unique identifier used to associate each element (value) in a map.
- Value: The elements associated with keys in a map.
Navigating with NavigableMap Methods
As a type of SortedMap, NavigableMap inherits all the methods from SortedMap. However, some of these methods are defined differently in NavigableMap. Let’s explore these methods in more detail:
Head, Tail, and SubMaps
- headMap(key, booleanValue): Returns all entries associated with keys before the specified key. The booleanValue parameter determines whether the specified key is included.
- tailMap(key, booleanValue): Returns all entries associated with keys after the specified key, including the entry associated with the key itself. Again, the booleanValue parameter determines whether the specified key is included.
- subMap(k1, bv1, k2, bv2): Returns all entries associated with keys between k1 and k2, including the entry associated with k1. The bv1 and bv2 parameters determine whether the entries associated with k1 and k2 are included.
Other NavigableMap Methods
- descendingMap(): Reverses the order of entries in a map.
- descendingKeySet(): Reverses the order of keys in a map.
- ceilingEntry(), ceilingKey(), floorEntry(), floorKey(), higherEntry(), higherKey(), lowerEntry(), and lowerKey(): These methods help you locate specific entries in a map based on their keys.
- firstEntry(), lastEntry(), pollFirstEntry(), and pollLastEntry(): These methods allow you to access and manipulate the first and last entries in a map.
Implementation in TreeMap Class
Now that you know about the NavigableMap interface, it’s time to learn how to implement it using the TreeMap class. We’ll cover this in more detail in our next tutorial.