Java TreeMap: Understanding Key-Value Insertion and Retrieval

Understanding TreeMap and Key-Value Pairs in Java

This code snippet demonstrates a key concept in Java's TreeMap data structure. Let's break down the code to understand how it works:

Map<String, String> dataMap = new TreeMap<String, String>();
dataMap.put('tom', 'from batch 01');
dataMap.put('ierry', 'from batch 01');
dataMap.put('linda', 'from batch 01');
dataMap.put('tom', 'from batch 02');
System.out.println(dataMap.get('tom'));

Explanation:

1. TreeMap Initialization: The code creates a TreeMap called dataMap to store key-value pairs, where the keys are String objects and the values are also String objects.
2. Key-Value Insertion: The put() method is used to insert key-value pairs into the TreeMap. Notice that the key 'tom' is used twice, first with the value 'from batch 01' and then with the value 'from batch 02'.
3. TreeMap's Behavior: TreeMap maintains a sorted order of keys. However, it allows duplicate keys. When a key is inserted multiple times, the TreeMap stores only the latest value associated with that key.
4. Retrieving the Value: The get() method retrieves the value associated with the key 'tom'. Since the latest value associated with 'tom' is 'from batch 02', the output will be:

Output:

B from batch02

Key Takeaway:

The TreeMap in Java handles duplicate keys by only storing the latest value associated with the key. This behavior can be useful for scenarios where you want to maintain a record of the most recent data associated with a particular key.