TreeSet, TreeMap vs HashSet, HashMap

Which data structure should be used in which situation!

TL;DR

• Unless there is a special reason, use HashMap which has good search performance

• If you want to guarantee order, use LinkedHashMap

• If you want to iterate over key values in a consistent manner, use TreeMap

Differences Between TreeMap and HashMap

• TreeMap is a data structure similar to HashMap, but the difference is that TreeMap's data is sorted

• Since HashMap's data is not sorted, it may be slower than TreeMap for data searching

• However, HashMap uses less memory than TreeMap

Order Guarantee Aspect

• HashMap does not guarantee order

  • LinkedHashMap guarantees the order of insertion!

• TreeMap guarantees order using the comparison operation of the class used as the Key value

  • It automatically sorts based on the key value

Speed Aspect

• The time complexity of HashMap is O(1)

  • Because it uses hash values

• The time complexity of TreeMap is O(log n)

  • In return, you can get a sorted order

Whether null is Allowed as a Key

• HashMap allows null as a key

• TreeMap does not allow null as a key

When to Use TreeMap?

• When you need to store and search ordered data

  • It has synchronization handling, making it Thread-safe

• When you need to search data in sorted order

• When insertion, deletion, and search operations on data are frequently performed

Cases Where TreeMap is Not Efficient

• When the data size is very large

• When insertion, deletion, and search operations on data are not frequently performed