How to Maintain Insertion Order in a Java HashMap?

Preserve Insertion Order in HashMap

The HashMap data structure in Java is designed to provide efficient storage and retrieval of key-value pairs. However, it does not maintain the insertion order of the elements. This can be problematic when the order of elements is significant.

LinkedHashMap: Maintaining Insertion Order

To preserve the insertion order, you can use the LinkedHashMap class. It extends the HashMap class and adds an additional feature: it maintains the order of the elements based on their insertion.

Using LinkedHashMap

To preserve the insertion order, simply replace HashMap with LinkedHashMap in your code:

<code class="java">Map<String, String> map = new LinkedHashMap<>();
map.put("first", "value1");
map.put("second", "value2");

for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println(entry.getKey() + " = " + entry.getValue());
}</code>

This code will now iterate over the map in the order in which the elements were inserted (i.e., "first" followed by "second").

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