How does Java order items in a HashMap or a HashTable?

by

java.util.HashMap is unordered; you can’t and shouldn’t assume anything beyond that.

This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time.

java.util.LinkedHashMap uses insertion-order.

This implementation differs from HashMap in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is normally the order in which keys were inserted into the map (insertion-order).

java.util.TreeMap, a SortedMap, uses either natural or custom ordering of the keys.

The map is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time, depending on which constructor is used.

More Related Contents:

  1. What are the differences between a HashMap and a Hashtable in Java?
  2. How does a Java HashMap handle different objects with the same hash code?
  3. Understanding the workings of equals and hashCode in a HashMap
  4. Good Hash Function for Strings
  5. What happens when a duplicate key is put into a HashMap?
  6. Does Java have a HashMap with reverse lookup?
  7. “Cannot create generic array of ..” – how to create an Array of Map?
  8. Java HashMap performance optimization / alternative
  9. ConcurrentHashMap and Hashtable in Java [duplicate]
  10. Why does HashMap require that the initial capacity be a power of two?
  11. How can I iterate over a map of ?
  12. What exactly is bucket in hashmap?
  13. How to create a HashMap with two keys (Key-Pair, Value)?
  14. Why Hashtable does not allow null keys or values?
  15. How to loop through a HashMap in JSP?
  16. How can I convert JSON to a HashMap using Gson?
  17. How to sort a HashMap in Java [duplicate]
  18. Is a HashMap thread-safe for different keys?
  19. Why there is no ConcurrentHashSet against ConcurrentHashMap
  20. Can an array be used as a HashMap key?
  21. How to get the unique ID of an object which overrides hashCode()?
  22. What is the optimal capacity and load factor for a fixed-size HashMap?
  23. Why does LinkedHashSet extend HashSet and implement Set
  24. what is the difference between == operator and equals()? (with hashcode() ???)
  25. Java: how to convert HashMap to array
  26. Android – Get value from HashMap
  27. Hashtable key within integer interval
  28. Spring can’t autowire Map bean
  29. Comparing two hashmaps for equal values and same key sets?
  30. Explanation of HashMap#hash(int) method

Leave a Comment