How Can I Maintain Insertion Order in a HashMap in Java?

Preserving Insertion Order in HashMap

When working with HashMaps in Java, the order in which elements are returned during iteration is often random, despite the order in which they were inserted. However, maintaining the insertion order can be crucial in certain scenarios.

The solution to preserving insertion order lies in using LinkedHashMap, which extends HashMap. Unlike HashMap, LinkedHashMap maintains the order of the inserted elements. When iterating over a LinkedHashMap, the key-value pairs are returned in the order they were added.

The syntax for creating and using LinkedHashMap is similar to HashMap:

<code class="java">Map<Key, Value> map = new LinkedHashMap<>();

// Add key-value pairs in the desired order
map.put(key1, value1);
map.put(key2, value2);

// Iterate over the map
for (Map.Entry<Key, Value> entry : map.entrySet()) {
    // Key and value are now accessible in the insertion order
}</code>

By leveraging LinkedHashMap, you can ensure that the insertion order of elements is preserved, regardless of the iteration order.

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