Introduction
Java is one of the most sought-after programming languages for web and enterprise application development. If you are pursuing Java learning online or aiming to become a Java Full Stack Developer, mastering Java collections is essential. Among Java’s collection framework, TreeMap is an important data structure widely used in applications requiring key-value pairs with sorted keys.
In this comprehensive guide, we will explore TreeMap in Java in-depth, covering its features, real-world applications, coding examples, and best practices. Whether you are taking online courses for Java or brushing up on your knowledge, this guide will help you understand and implement TreeMap efficiently.
It can be as challenging to understand when and how to use a Java TreeMap as it is to navigate a dense forest, with each turn revealing something new.
But as with any worthwhile endeavour, having the correct tools on hand makes everything simpler; and with TreeMap in Java, you’ll have exactly what you need to navigate around.
We’ll examine what a Java TreeMap is in this article and go over its benefits over other data structures. We’ll also look at illustrations of its application in actual-world situations. Check out our free Java course with certificate to learn more about TreeMap in Java, how it works, and how it is related to HashMap and LinkedHashMap.
What is TreeMap in Java?
TreeMap is a part of Java’s java.util package and implements the NavigableMap interface, which extends SortedMap. Unlike HashMap, which offers constant-time complexity for basic operations, TreeMap maintains the keys in sorted order based on their natural ordering or a custom comparator.
A data structure for storing and organising things according to key-value pairs is called a Java TreeMap in Java. It offers rapid ways to seek particular elements and effective ways to discover what keys are connected to an element. It is comparable to a hash map, except it also preserves the order in which the objects were inserted.
TreeMap is an implementation of NavigableMap based on Red-Black trees. It is arranged in the order that its keys naturally appear. Similar to the HashMap class, the TreeMap class implements the Map interface. The primary distinction between both is that TreeMap is sorted in the ascending order of its keys, whereas HashMap is an unordered collection. Because TreeMap in Java is an unsynchronized collection type, thread-safe operations cannot be performed on it until and unless synchronised explicitly
A TreeMap’s root node is made up of sub-nodes (map components) that can either be keys or values. Each node in the tree contains a parent and a child, indicating that it is hierarchical. This makes it simple to quickly and simply access various areas of the map.
Advantages of Using Java TreeMaps
Compared to more traditional data structures like HashMaps, Arrays, and Linked Lists, Java TreeMaps provides a few advantages. They can hold an infinite amount of key-value pairs without degrading performance, for starters. Because they are not required to retain pointers to other objects, they consume less memory than conventional data structures.
Java TreeMaps are also incredibly easy to search through, which makes them perfect for applications that need quick access. They also provide a simple method for grouping components based on their keys, values, or both. As a result, information pertaining to a specific key or value can be rapidly found.
Key Features of TreeMap:
- Sorted Order: Automatically arranges keys in ascending order.
- No Duplicate Keys: Each key must be unique.
- Red-Black Tree Implementation: Internally uses a balanced binary search tree.
- Efficient Retrieval: Provides O(log n) complexity for get, put, and remove operations.
- NavigableMap Functions: Supports methods like firstEntry(), lastEntry(), lowerEntry(), and higherEntry().
When should you use Java TreeMaps?
TreeMap in Java are useful for many different activities. Here are a few typical instances:
- Keeping coordinates for locations to be plotted on a map: Java’s built-in tree structure makes it simple to store and access location information like latitude and longitude.
- Genre-based categorization of music files: TreeMap in Java make it simple to store and arrange music files so that users can quickly locate what they’re looking for.
- Making complex databases searchable: Java TreeMaps can make databases that are simple to query and browse through.
Java TreeMap Examples
1. Creating a Java TreeMap
We can make a new TreeMap in Java object in this example and add two entries. The map is then printed out to show what is on it.
2. Retrieving an Entry from a Java TreeMap
In this case, we may receive the value linked to a certain key using the get() method. In this instance, the output will be “value1”.
3. Iterating Through the Java TreeMap
To print out all the keys on the map in this example, we may go over them all using the for-each loop.
4. Default Sorting
Additionally, you can group elements into categories and order them based on their keys or values. The components are organised alphabetically by their keys.
5. Custom Sorting
Custom sorting is another option. In this example, a custom Comparator object is used to order the items according to their values.
Which map should you use (HashMap, LinkedHashMap, or TreeMap?
Your specific use case and the kinds of procedures you require will determine the answer to this inquiry. Use HashMap for quick lookups if you require them. Use LinkedHashMap in java if you need an insertion order or access order. Use TreeMap in Java to sort keys.
Data storage, organisation, and retrieval can be made simple with Java TreeMaps, a fantastic tool. You may build intricate databases using TreeMaps that are simple to query and search through. Additionally, you can build custom sorting or use default sorting based on your requirements.
How to Create a TreeMap in Java
To use TreeMap, you need to import java.util.TreeMap
. Below is a basic example music files the creation and manipulation of a TreeMap:
import java.util.*;
public class TreeMapExample {
public static void main(String[] args) {
// Creating a TreeMap
TreeMap<Integer, String> treeMap = new TreeMap<>();
// Adding elements
treeMap.put(101, "John");
treeMap.put(103, "Alice");
treeMap.put(102, "Bob");
treeMap.put(104, "David");
// Printing TreeMap
System.out.println("TreeMap: " + treeMap);
}
}
Output:
TreeMap: {101=John, 102=Bob, 103=Alice, 104=David}
Notice that TreeMap maintains the keys in ascending order automatically.
Real-World Applications of TreeMap
1. Banking Systems:
TreeMap is commonly used in banking applications to maintain sorted records of transactions based on timestamps.
2. Scheduling Algorithms:
Job scheduling and task prioritization systems use TreeMap to organize tasks based on priority levels.
3. E-Commerce Applications:
E-commerce platforms sort products based on price or availability using TreeMap.
4. DNS Caching:
TreeMap is used in domain name system (DNS) caching to maintain records in a sorted order.
NavigableMap Functions in TreeMap
TreeMap implements the NavigableMap interface, which provides additional functionalities for navigation.
Example: Navigating Through TreeMap
import java.util.*;
public class TreeMapNavigation {
public static void main(String[] args) {
TreeMap<Integer, String> students = new TreeMap<>();
students.put(101, "John");
students.put(103, "Alice");
students.put(105, "Bob");
students.put(107, "David");
System.out.println("First Entry: " + students.firstEntry());
System.out.println("Last Entry: " + students.lastEntry());
System.out.println("Lower Entry (before 105): " + students.lowerEntry(105));
System.out.println("Higher Entry (after 105): " + students.higherEntry(105));
}
}
Output:
First Entry: 101=John
Last Entry: 107=David
Lower Entry (before 105): 103=Alice
Higher Entry (after 105): 107=David
Custom Sorting with TreeMap
By default, TreeMap sorts keys in their natural order. However, you can use a custom Comparator to define a different sorting order.
Example: Sorting Keys in Descending Order
import java.util.*;
public class TreeMapCustomSorting {
public static void main(String[] args) {
TreeMap<Integer, String> descendingMap = new TreeMap<>(Collections.reverseOrder());
descendingMap.put(101, "John");
descendingMap.put(103, "Alice");
descendingMap.put(105, "Bob");
descendingMap.put(107, "David");
System.out.println("TreeMap in Descending Order: " + descendingMap);
}
}
Output:
TreeMap in Descending Order: {107=David, 105=Bob, 103=Alice, 101=John}
Best Practices for Using TreeMap
- Use TreeMap only when sorting is required. If sorting is not needed, consider using HashMap for better performance.
- Avoid storing null keys. TreeMap does not allow null keys but permits multiple null values.
- Optimize performance by limiting TreeMap size. Large TreeMaps can impact performance due to log(n) complexity.
- Use TreeMap in real-time applications where data retrieval in sorted order is necessary.
Key Takeaways
- TreeMap maintains a sorted order of keys automatically.
- It is implemented using Red-Black Trees, ensuring logarithmic time complexity for operations.
- It is beneficial in applications requiring natural ordering of data.
- NavigableMap features enhance searching, filtering, and traversal capabilities.
- Custom sorting can be achieved using Comparator.
Conclusion
TreeMap is a powerful Java collection that ensures sorted key-value storage, making it ideal for various applications. If you are looking to enhance your Java Full Stack Developer skills, mastering TreeMap is essential.
Want to learn Java in-depth? Join H2K Infosys‘ online course for Java today and gain hands-on experience in Java development!