Stop, think about it. Are you using the right Data Structure?

A very trivial thing but knowing which data structure or implementation maintains the order of insertion, allows duplicates, or does not accept null helps prevent unexpected outcomes. Had a similar first-hand experience a few months ago. 💀

For example, lets take Map interface. There are three classes that implements Map in java - HashMap, LinkedHashMap and TreeMap.

♨️ HashMap doesn't maintain insertion order, LinkedHashMap does, TreeMap maintains order in sorted manner.
♨️ HashMap and LinkedHashMap allows one null key object (K,V), TreeMap doesn't (it may have multiple null values, never the keys).
♨️ HashMap and LinkedHashMap both have O(1) insertion and search. TreeMap, has O(logN). Bonus - TreeMap is implemented using RB-Tree, HM - LinkedLists, LHM - Doubley-LL. These implementation are the reason for these TC.