#35 | Sort Map by Keys / Values | Java Interview | Recently Asked Questions

In this video, we explain how to sort a Map by keys and values in Java — a very common Core Java and interview question that tests your understanding of collections, ordering, and design choices.

You’ll learn why a Map cannot be sorted directly, and the correct, interview-approved ways to sort it using different approaches.

👨‍💻 What you’ll learn:

Why Map can’t be sorted directly
• Map does not maintain order by default
• Sorting requires comparison logic, which Map itself doesn’t provide
• So we first convert Map data into a sortable structure and then store it back

Sorting Map by Keys

Using TreeMap
• TreeMap automatically sorts entries by keys
• Uses natural ordering or a custom Comparator
• Best and simplest approach when key-based sorting is required

Descending Order by Keys
• TreeMap can also sort keys in reverse order using a Comparator

Using Streams
• Convert Map to a stream of entries
• Sort entries by key
• Collect into LinkedHashMap to preserve sorted order

Sorting Map by Values

• Maps do NOT support value-based sorting directly
• TreeMap cannot be used for value sorting

Using List + Comparator
• Convert Map entrySet into a List
• Sort the list using a Comparator on values
• Store results in LinkedHashMap to maintain order

Using Streams
• Convert Map to stream
• Sort entries by value
• Collect into LinkedHashMap to preserve order

🎯 What interviewers expect:
• You know Map cannot be sorted directly
• You understand TreeMap sorts by keys, not values
• You can explain why LinkedHashMap is used to preserve order
• You can choose the right approach based on keys vs values

🧠 How you should answer in interviews:
Maps cannot be sorted directly because they don’t maintain order. To sort by keys, we use TreeMap or streams. To sort by values, we convert entries into a list or stream, apply a comparator, and store the result in a LinkedHashMap to preserve order.

This video is perfect for Core Java interviews, backend development, and mastering Java Collections.

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