Java Treemap Tutorial: Ten Illustration Of Treemap Inward Java
Friday, June 22, 2018
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TreeMap inwards Java is a SortedMap as well as it maintains Sorting gild when you lot insert object on it.
You tin specify Sorting gild spell Creating TreeMap past times providing an explicit Comparator to
TreeMap. Basically you lot tin practice TreeMap inwards Java past times dissimilar ways, a TreeMap amongst natural sorting order, as well as TreeMap amongst custom Sorting Order past times providing Comparator, Copying Sorting gild from other SortedMap etc. TreeMap has specific constructor for these conditions. We volition run across these inwards department of creating illustration of TreeMap inwards Java. We volition equally good run across how to lay element, instruct element, iterate over TreeMap, clearing as well as reusing TreeMap inwards this Java TreeMap tutorial. This article is inwards continuation of my collection serial e.g. HashMap vs HashSet , SynchronziedHashMap vs ConcurrentHashMap and Iterator vs Enumeration inwards Java
Java TreeMap Tutorial as well as Example
Creating TreeMap inwards Java using natural ordering of keys
Here are few ways to practice TreeMap inwards Java:
TreeMap inwards Java using natural ordering of keys
TreeMap naturalOrderMap = novel TreeMap();
TreeMap amongst custom sorting order
TreeMap customSortingMap = novel TreeMap(Comparator comparator)
Objects stored inwards this TreeMap volition live ordered according to given Comparator.
TreeMap from existing SortedMap
TreeMap sameOrderMap = novel TreeMap(SortedMap sm)
This TreeMap volition convey the same mappings as well as gild equally specified past times provided SortedMap. TreeMap is similar to HashMap inwards Java equally both implements Map interface amongst divergence inwards that fundamental inwards TreeMap are sorted.
Add object into TreeMap inwards Java
Now inserting or adding object into TreeMap is really simple, you lot involve to utilisation same put(key, value) method which is available shape Map. Below is an illustration of putting objects into TreeMap. What is of import hither is that TreeMap sorts object equally presently equally 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 inwards Cash equally good called Cash Equity");
assetClassMap.put("Derivative", "Derivative is by as well as large futures, options trading ");
assetClassMap.put("Foriegn Exchange", "FX is converting currency from 1 to other e.g. USD to YEN");
Retrieve object from TreeMap
Simple simply utilisation get(key) method as well as render fundamental as well as it volition render value shape TreeMap.
assetClassMap.get("Equity");
assetClassMap.get("Derivative");
How to clear TreeMap inwards Java
You tin reuse same TreeMap for dissimilar role past times clearing it. clear() will take away all entries from TreeMap as well as piece of job into empty. Beware of clearing Map inwards multi-threading environment where it could live possible that before you lot clear another thread read one-time values.
assetClassMap.clear();
How to instruct Comparator from TreeMap
If you lot convey created TreeMap inwards Java past times providing an external comparator than you lot tin instruct that
Comparator past times comparator() method of TreeMap. But if you lot are sorting values past times natural gild this method volition render null.
Comparator comparator = assetClassMap.comparator();
Checking a value exists inwards Java TreeMap
Sometime nosotros desire to run across whether a item value exists inwards TreeMap or not, this is quite slow past times using utility method containsValue(Object value) of TreeMap class inwards 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 lucifer a fundamental exists inwards TreeMap
Just similar checking for values inwards treeMap inwards Java you lot tin equally good search for keys past times using method containsKey this method volition render truthful if you lot comprise specified fundamental or render imitation if TreeMap doesn't contains that key.
assetClassMap.containsKey("Derivatives");
How to instruct a opposite gild thought of Mapping from TreeMap
From jdk 1.6 onwards you lot tin instruct a opposite gild thought of mapping contains inwards TreeMap inwards Java past times using method descendingMap() which returns a NaviagableMap. descendingMap is backed past times master copy TreeMap as well as nay modify inwards either of Map volition reverberate at both places.if whatever of TreeMap modified during an iteration except through Java iterator's take away method number of the iteration is undefined.'
NavigableMap reverseTreeMap = assetClassMap.descendingMap();
You tin equally good instruct opposite gild treeMap past times using Collections.reverseOrder(Comparator) which is available from Java5 onwards. Similarly you lot tin equally good instruct descending keySet past times calling method descendingKeySet which returns a NavigableSet amongst opposite orders of key. Read to a greater extent than close Comparator as well as comparable in Java here.
How to instruct get-go entry from TreeMap inwards Java
Since TreeMap is a SortedMap nosotros tin instruct both get-go as well as terminal entry from TreeMap. TreeMap in
Java provides convenient method to instruct firstKey as well as lastKey from TreeMap. Below is illustration of TreeMap as well as getting get-go fundamental as well as get-go entry. FirstKeywill throw NoSuchElementException exception if TreeMap is empty spell firstEntry volition render null.
assetClassMap.firstEntry();
assetClassMap.firstKey();
How to instruct terminal entry from Java TreeMap
Similar to to a higher house illustration of getting get-go entry as well as get-go fundamental you lot tin equally good instruct terminal entry as well as lastkey from treeMap inwards Java equally shown inwards below Exmaple of TreeMap.Similar to firstKey as well as firstEntry inwards TreeMap lastkey volition throw NoSuchElementException if TreeMap is empty spell lastEntry volition simply render null.
assetClassMap.lastEntry();
assetClassMap.lastKey();
Similar to before illustration of getting get-go entry from treeMap inwards Java. You tin equally good instruct terminal entry from Java TreeMap.
Creating subMap from TreeMap inwards Java
From JDK 1.6 onwards nosotros convey a subMap() method inwards TreeMap which returns part of Map spell fundamental make is specified past times fromKey to toKey. The returned Map is backed past times master copy TreeMap as well as whatever modify made inwards subMap volition reverberate dorsum inwards TreeMap as well as vice-versa.Returned subMap equally good supports all optional Map operations that this Map supports. SubMap volition throw as well as IllegalArgumentException when you lot insert a fundamental exterior of its range.
SortedMap subMap = assetClassMap.subMap("Derivative", "Foriegn Exchange");
Creating headMap as well as tailMap from TreeMap inwards Java
Inline amongst to a higher house illustration of getting SubMap from TreeMap you lot tin equally good instruct headMap as well as tailMap from treeMap on Java6 onwards.headMap(K toKey,boolean inclusive) is used to instruct headMap which is a business office 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 illustration of headMap as well as tailMap, headTreeMap volition comprise null elements because "Derivative" is lowest fundamental as well as in that location is no fundamental 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 telephone substitution is greater than Derivatives.
Checking whether TreeMap is empty
There is convinient isEmpty()method from AbstactMap which is used to banking concern lucifer whether TreeMap inwards coffee is empty or not, its render truthful if TreeMap doesn't comprise whatever entry.
boolean isEmpty = assetClassMap.isEmpty();
How to respect Size of TreeMap inwards Java
TreeMap inwards coffee provides a size() method which tin live used to instruct full number of elements inwards Java.
int size = assetClassMap.size();
Removing objects from TreeMap inwards Java
remove(Object key) method is used to take away whatever mapping from Java TreeMap. Don’t utilisation this spell iterating, instead utilisation iterator's remove() method.
assetClassMap.remove("Equity");
That's all on TreeMap inwards Java. Please enhance whatever enquiry or doubts you lot convey on using TreeMap inwards Java or whatever Example of Java TreeMap as well as nosotros volition run across how nosotros tin solve that. In Summary TreeMap inwards Java is an of import Collection class as well as pretty useful for Sorting.
Further Learning
Java In-Depth: Become a Complete Java Engineer
How to debug Java Program inwards Eclipse – Tips
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