Using LinkedHashMap in Java to Remove Duplicates and Preserve Order

Learn how to use LinkedHashMap in Java to eliminate duplicates from a list while preserving the original order of the records.
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When working with collections in Java, it's not uncommon to encounter scenarios where you need to remove duplicates from a list but also maintain the original order of the records. The LinkedHashMap class from the Java Collections Framework provides an efficient solution for this exact problem.

The LinkedHashMap not only prevents duplicates but also maintains the insertion order. This makes it ideal for converting a list with potential duplicates into a collection of unique items, while still keeping their initial sequence intact. Here’s how you can achieve this:

Step-by-Step Guide

Create a List with Duplicates

First, you need a list that contains duplicate entries.

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Use LinkedHashMap to Remove Duplicates

Initialize a LinkedHashMap which will store the list items as keys. This automatically removes duplicates because keys in a map are unique.

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Convert Map Keys Back to List

Once you've populated the LinkedHashMap, convert its keys back into a list. This final list will have duplicates removed and the original order preserved.

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Complete Example

Here's the entire process in a single Java program:

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Conclusion

By utilizing a LinkedHashMap in Java, you can effectively remove duplicates from a list while preserving the order of records as they were originally inserted. This method is straightforward, leveraging the unique properties of maps and the order-preserving nature of a LinkedHashMap.