flowchart TD
A[Do you need key–value pairs?] -->|Yes| B[Use a Map]
A -->|No| C[Need unique elements?]
B --> B1[Fast lookup] ----> B1a[HashMap]
B --> B2[Preserve insertion order] ----> B21[inkedHashMap]
B2 --> B2a[LRU cache] ---> B2a1[LinkedHashMap accessOrder=true]
B --> B3[Sorted keys] ----> B3a[TreeMap]
B --> B4[Thread safety]
B4 ----> B41[ConcurrentHashMap]
B4 --> B42[Sorted + concurrent] ---> B42a[ConcurrentSkipListMap]
B --> B5[GC-sensitive cache] ----> B5a[WeakHashMap]
B --> B6[Enum keys] ----> B6a[EnumMap]
C -->|Yes| D[Use a Set]
C -->|No| E[Use a List]
D --> D1[Fast lookup] ---> D1a[HashSet]
D --> D2[Preserve insertion order] ---> D2a[LinkedHashSet]
D --> D3[Sorted elements] ---> D3a[TreeSet]
D --> D4[Thread safety?]
D4 --> D42[Read-mostly?] --> |Yes|D42a[CopyOnWriteArraySet]
D42 --> |NO| D41[ConcurrentSkipListSet]
D --> D5[Enum elements] ---> D5a[numSet]
E --> E1[Fast random access] ---> E1a[ArrayList]
E --> E2[Frequent inserts/removes] ---> E2a[LinkedList]
E --> E3[Thread safety]
E3 --> E31[Read-mostly] --> E31a[CopyOnWriteArrayList]
E3 --> E32[Legacy] --> E32a[Vector/Stack]
E --> F[Need queue/stack behavior?]
F --> F3[Thread safety?]
%% Special cases
A --> S[Special cases]
S --> S1[Compare by identity] ----> S1a[IdentityHashMap]
S --> S2[Bitset-like enums] ----> S2a[EnumSet]
