# Collection Framework Cheat Sheet
| Collection Classes |
Duplicates Accepted? |
Insertion Order maintained? |
Sorted Order? |
Is Thread Safe? |
| **List ** |
| ArrayList |
**Yes** |
**Yes** |
No |
No |
| LinkeList |
**Yes** |
**Yes** |
No |
No |
| Vector |
**Yes** |
**Yes** |
No |
**Yes** |
| **Set** |
| HashSet |
No |
No |
No |
No |
| LinkedHashSet |
No |
**Yes** |
No |
No |
| TreeSet |
No |
**Yes** |
**Yes** |
No |
| **Map** |
| HashMap |
No |
No |
No |
No |
| LinkedHashMap |
No |
**Yes** |
No |
No |
| Hashtable |
No |
No |
No |
**Yes** |
| TreeMap |
No |
**Yes** |
**Yes** |
No |
- *All lists* allow duplicate elements and follow *insertion order*.
- All *list* elements are *not sorted*.
- All sets and maps do not allow duplicate elements.
- *Sets *and *maps *do *not sort *their elements, *except TreeSet and TreeMap* – in which elements are sorted by natural order or by a comparator.
- Elements within *sets and maps *are *not ordered*, except for:
- *LinkedHashSet *and *LinkedHashMap *have elements *ordered by insertion order*.
- *TreeSet *and *TreeMap *have elements ordered by *natural order or by a comparator*.
- There are only *two collections *that are *thread-safe*: *Vector *and *Hashtable*. The rest is not thread-safe.
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-- **P**asumarthi **S**ai **P**hani **K**rishna (aka PSPK)😊