Treemap sort by value
For a quick solution to sort a TreeMap
by their values, follow these steps:
- Convert
entrySet
to a Stream - Sort it using a custom
Comparator
derived fromMap.Entry.getValue()
- Gather the sorted entries into a
LinkedHashMap
to uphold the order.
Here's how you do it in Java:
Voila! You now have a LinkedHashMap
that's sorted by the TreeMap’s values.
Busting TreeMap myths: Why it doesn’t sort by value
Ever wondered why a TreeMap
doesn't naturally sort by value? The TreeMap
class in Java, being a dutiful child of the SortedMap
interface, keeps the order aligned to key comparisons. Sorting by value? That's a rebel act for TreeMap – it not only violates the SortedMap
spec but also can introduce unexpected behavior.
How to break free: Sorting TreeMap by values
Custom Comparator: Time to compare apples to apples
This is where a custom Comparator
comes to play! Create your custom Comparator to compare Map.Entry
objects based on their values:
Advisory: Beware of the trap while dealing with Integer
types. The '==' operator is a wolf in sheep clothing. Always use .equals()
for Integer value equality.
The Immutable Guard: Handling TreeMap modification
Remember, treating the original TreeMap or SortedSet as a rag doll can cause complications. So, once you’ve converted the sorted entries into a LinkedHashMap
, any subsequent modification should be made on this new map. If you still feel nostalgic about your old TreeMap
, re-run the sorting operation after changes.
Considerations & Alternatives: Is there another way to Mordor?
The Stream Chalice: Leverage java streams
Been a java 8 user? You can now turn into a waterbender by manipulating streams to dictate the TreeMap
value sorting process. Want to change the rules? Add Comparator.reverseOrder()
and watch the magic happen!
Value sorting with Persistence: LinkedHashMap
Here's a hack: After sorting, use a LinkedHashMap
to make insertion order persistent. Now that’s a core component to sustain the value-sorting intact!
Uniqueness Matter: Handling the Clones
Meet the clone troopers - duplicate values. While sorting by values, they might pose as hurdles in preserving uniqueness. In cases of duplicates, the merge function (e1, e2) -> e1
used in .collect()
, helps to upkeep the first entry met. Now, that’s service towards the TreeMap's ordering contract!
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