TreeMap inward Java is a SortedMap as well as it maintains Sorting lodge when you lot insert object on it.
You tin plough over the sack specify Sorting lodge spell Creating TreeMap yesteryear providing an explicit Comparator to
TreeMap. Basically you lot tin plough over the sack practice TreeMap inward Java yesteryear dissimilar ways, a TreeMap amongst natural sorting order, as well as TreeMap amongst custom Sorting Order yesteryear providing Comparator, Copying Sorting lodge from other SortedMap etc. TreeMap has specific constructor for these conditions. We volition meet these inward department of creating representative of TreeMap inward Java. We volition too meet how to lay element, larn element, iterate over TreeMap, clearing as well as reusing TreeMap inward this Java TreeMap tutorial. This article is inward continuation of my collection serial e.g. HashMap vs HashSet , SynchronziedHashMap vs ConcurrentHashMap and Iterator vs Enumeration inward Java
Java TreeMap Tutorial as well as Example
Creating TreeMap inward Java using natural ordering of keys
Here are few ways to practice TreeMap inward Java:
TreeMap inward Java using natural ordering of keys
TreeMap naturalOrderMap = novel TreeMap();
TreeMap amongst custom sorting order
TreeMap customSortingMap = novel TreeMap(Comparator comparator)
Objects stored inward this TreeMap volition live ordered according to given Comparator.
TreeMap from existing SortedMap
TreeMap sameOrderMap = novel TreeMap(SortedMap sm)
This TreeMap volition accept the same mappings as well as lodge every bit specified yesteryear provided SortedMap. TreeMap is similar to HashMap inward Java every bit both implements Map interface amongst departure inward that primal inward TreeMap are sorted.
Add object into TreeMap inward Java
Now inserting or adding object into TreeMap is real simple, you lot involve to utilization same put(key, value) method which is available shape Map. Below is an representative of putting objects into TreeMap. What is of import hither is that TreeMap sorts object every bit presently every bit you lot insert them as well as throws ClassCastException if novel object is non convertible into type of Object TreeMap is holding. assetClassMap.put("Fixed Income", "Fixed income is related to bonds, Fixed Deposit, Swaps etc");
assetClassMap.put("Equity", "Equity is related to Stock trading inward Cash too called Cash Equity");
assetClassMap.put("Derivative", "Derivative is generally futures, options trading ");
assetClassMap.put("Foriegn Exchange", "FX is converting currency from i to other e.g. USD to YEN");
Retrieve object from TreeMap
Simple simply utilization get(key) method as well as render primal as well as it volition render value shape TreeMap.
assetClassMap.get("Equity");
assetClassMap.get("Derivative");
How to clear TreeMap inward Java
You tin plough over the sack reuse same TreeMap for dissimilar utilization yesteryear clearing it. clear() will take away all entries from TreeMap as well as motion into empty. Beware of clearing Map inward multi-threading environment where it could live possible that before you lot clear another thread read erstwhile values.
assetClassMap.clear();
How to larn Comparator from TreeMap
If you lot accept created TreeMap inward Java yesteryear providing an external comparator than you lot tin plough over the sack larn that
Comparator yesteryear comparator() method of TreeMap. But if you lot are sorting values yesteryear natural lodge this method volition render null.
Comparator comparator = assetClassMap.comparator();
Checking a value exists inward Java TreeMap
Sometime nosotros desire to meet whether a detail value exists inward TreeMap or not, this is quite slow yesteryear using utility method containsValue(Object value) of TreeMap class inward Java. This method returns truthful if TreeMap contains specified value otherwise render false.
assetClassMap.containsValue("does it comprise equities trading info");
How to banking concern jibe a primal exists inward TreeMap
Just similar checking for values inward treeMap inward Java you lot tin plough over the sack too search for keys yesteryear using method containsKey this method volition render truthful if you lot comprise specified primal or render faux if TreeMap doesn't contains that key.
assetClassMap.containsKey("Derivatives");
How to larn a contrary lodge persuasion of Mapping from TreeMap
From jdk 1.6 onwards you lot tin plough over the sack larn a contrary lodge persuasion of mapping contains inward TreeMap inward Java yesteryear using method descendingMap() which returns a NaviagableMap. descendingMap is backed yesteryear master copy TreeMap as well as nay alter inward either of Map volition reverberate at both places.if whatever of TreeMap modified during an iteration except through Java iterator's take away method effect of the iteration is undefined.'
NavigableMap reverseTreeMap = assetClassMap.descendingMap();
You tin plough over the sack too larn contrary lodge treeMap yesteryear using Collections.reverseOrder(Comparator) which is available from Java5 onwards. Similarly you lot tin plough over the sack too larn descending keySet yesteryear calling method descendingKeySet which returns a NavigableSet amongst contrary orders of key. Read to a greater extent than nearly Comparator as well as comparable in Java here.
How to larn commencement entry from TreeMap inward Java
Since TreeMap is a SortedMap nosotros tin plough over the sack larn both commencement as well as final entry from TreeMap. TreeMap in
Java provides convenient method to larn firstKey as well as lastKey from TreeMap. Below is representative of TreeMap as well as getting commencement primal as well as commencement entry. FirstKeywill throw NoSuchElementException exception if TreeMap is empty spell firstEntry volition render null.
assetClassMap.firstEntry();
assetClassMap.firstKey();
How to larn final entry from Java TreeMap
Similar to inward a higher house representative of getting commencement entry as well as commencement primal you lot tin plough over the sack too larn final entry as well as lastkey from treeMap inward Java every bit shown inward below Exmaple of TreeMap.Similar to firstKey as well as firstEntry inward TreeMap lastkey volition throw NoSuchElementException if TreeMap is empty spell lastEntry volition simply render null.
assetClassMap.lastEntry();
assetClassMap.lastKey();
Similar to before representative of getting commencement entry from treeMap inward Java. You tin plough over the sack too larn final entry from Java TreeMap.
Creating subMap from TreeMap inward Java
From JDK 1.6 onwards nosotros accept a subMap() method inward TreeMap which returns part of Map spell primal gain is specified yesteryear fromKey to toKey. The returned Map is backed yesteryear master copy TreeMap as well as whatever alter made inward subMap volition reverberate dorsum inward TreeMap as well as vice-versa.Returned subMap too supports all optional Map operations that this Map supports. SubMap volition throw as well as IllegalArgumentException when you lot insert a primal exterior of its range.
SortedMap subMap = assetClassMap.subMap("Derivative", "Foriegn Exchange");
Creating headMap as well as tailMap from TreeMap inward Java
Inline amongst inward a higher house representative of getting SubMap from TreeMap you lot tin plough over the sack too larn headMap as well as tailMap from treeMap on Java6 onwards.headMap(K toKey,boolean inclusive) is used to larn headMap which is a role of master copy Map whose keys are less than or equalto toKey. tailMap is opposite to headMap where keys are greater than(or equal to, if inclusive is true)fromKey
SortedMap headTreeMap = assetClassMap.headMap("Derivative");
SortedMap tailTreeMap = assetClassMap.tailMap("Derivative");
In Above representative of headMap as well as tailMap, headTreeMap volition comprise null elements because "Derivative" is lowest primal as well as at that spot is no primal which is less than that as well as tailTreeMap volition contains 4 entries because every other entries e.g. Equities, Fixed Income as well as unusual central is greater than Derivatives.
Checking whether TreeMap is empty
There is convinient isEmpty()method from AbstactMap which is used to banking concern jibe whether TreeMap inward coffee is empty or not, its render truthful if TreeMap doesn't comprise whatever entry.
boolean isEmpty = assetClassMap.isEmpty();
How to honor Size of TreeMap inward Java
TreeMap inward coffee provides a size() method which tin plough over the sack live used to larn full publish of elements inward Java.
int size = assetClassMap.size();
Removing objects from TreeMap inward Java
remove(Object key) method is used to take away whatever mapping from Java TreeMap. Don’t utilization this spell iterating, instead utilization iterator's remove() method.
assetClassMap.remove("Equity");
That's all on TreeMap inward Java. Please heighten whatever interrogation or doubts you lot accept on using TreeMap inward Java or whatever Example of Java TreeMap as well as nosotros volition meet how nosotros tin plough over the sack solve that. In Summary TreeMap inward Java is an of import Collection class as well as pretty useful for Sorting.
Further Learning
Java In-Depth: Become a Complete Java Engineer
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