Treemap In Java

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Hey guys!! Welcome to flower brackets. Today we are going to learn treemap in java.

Well let’s first understand what exactly term “map” means and then later we learn about treemap.

what is map?

Map is an object. In map we can store key value pair.

Treemap In Java

Here you can see the example of map. Here key is “Player Code” value is “Player Name”.

For key 01 corresponding value is Mahendra Singh dhoni, for key 02 corresponding value is virat kohli, for key 03 corresponding value is rohit sharma and for key 04 corresponding value is shikhar dhawan.

Read Also – Parameter Passing And Returning A Value From A Method In Java

Each row is called a key value pair. First key value pair is ( 01, Mahendra singh dhoni ), second key value pair is ( 02, Virat Kohli ), third key value pair is ( 03, rohit sharma ) and fourth key value pair is ( 03, shikhar dhawan ).

By default treemap will arrange the key value pairs in ascending order of keys. Using key we can identify the corresponding value. Each key value pair is called entry.

Key should be unique. We cannot put duplicate key in the map.


introduction: Treemap In Java

Treemap is used to store key value pair. Each row is called key value pair. By default treemap will arrange the key value pairs in ascending order.

Hierarchy of Treemap Class

Treemap In Java

Treemap class implements navigablemap interface. Navigablemap interface extends sortedmap interface. Sortedmap interface extends map interface.

Treemap class belongs to java.util package.

Class TreeMap< K,V >

Here you can see K comma V. K is a type of keys which we are planning to maintain in the treemap.

V is a type of values which we are planning to maintain in the treemap.

java.lang.Object
     java.util.AbstractMap<K,V>
          java.util.TreeMap<K,V>

Treemap class extends abstractmap class, abstractmap class extends object class.

Serializable, Cloneable, Map<K,V>, NavigableMap<K,V>, SortedMap<K,V>

And treemap class implements serializable interface, cloneable interface, map interface, navigablemap interface and sortedmap interface.

Treemap is used to store key and value pairs. For a given key we can find the corresponding value.

Key must be unique but the values can be duplicated. Treemap is same as hashmap.

The only difference is treemap maintains ascending order and treemap is sorted according to the natural ordering of its keys.

Treemap won’t allow null key but it will allow multiple null values. Treemap implementation is not synchronized and treemap is red black tree based navigablemap implementation.


Methods of treemap

Methods - modifierDescription
Map.Entry ceilingEntry(K key)Returns a key value mapping associated with the least key >= to the given key or null if there is no such key.
void clear()This method removes all the mappings from this map.
Object clone()This method returns a shallow copy of this TreeMap instance
Comparator comparator()Returns the comparator used to order the keys in this map or null if this map uses the natural ordering of its keys.
boolean containsKey(Object key)Returns true if this map contains a mapping for the specified key.
boolean containsValue(Object value)Returns true if this map contains a mapping for the specified value.
NavigableSet descendingKeySet()Returns a reverse order NavigableSet view of the keys contained in this map.
NavigableMap descendingMap()Returns a reverse order view of the mappings contained in this map.
Set> entrySet()Returns a Set() view of the mappings contained in this map.
Map.Entry firstEntry()Returns a key value mapping associated with the least key in this map or null if the map is empty.
K firstKey()Returns the first ( lowest ) key currently in this map.
Map.Entry floorEntry(K key)Returns a key value mapping associated with the greatest key <= the given key or null if there is no such key.
K floorKey(K key)Returns the greatest key <= the given key or null if there is no such key.
V get(Object key)Returns the value to which the specified key is mapped or null if this map contains no mapping for the key.
SortedMap headMap(K toKey)Returns a view of the portion of this map whose keys are strictly less than toKey.
NavigableMap headMap(K toKey, boolean inclusive)Returns a view of the portion of this map whose keys are less than ( or equal to, if inclusive is true ) toKey.
Map.Entry higherKey(K key)Returns a key-value mapping associated with the least key strictly greater than the given key or null if there is no such key.
K higherKey(K key)Returns the least key strictly greater than the given key or null if there is no such key.
Set keySet()Returns a Set view of the keys contained in this map.
Map.Entry lastEntry()Returns a key-value mapping associated with the greatest key in this map or null if the map is empty.
K lastKey()Returns the last(highest) key currently in this map.
Map.Entry lowerEntry(K key)Returns a key value mapping associated with the greatest key strictly less than the given key or null if there is no such key.
K lowerKey(K key)Returns the greatest key strictly less than the given key or null if there is no such key.
NavigableSet navigableKeySet()Returns a NavigableSet view of the keys contained in this map.
Map.Entry pollFirstEntry()Removes and returns a key value mapping associated with the least key in this map or null if the map is empty.
Map.Entry pollLastEntry()Removes and returns a key value mapping associated with the greatest key in this map or null if the map is empty.
V put(K key, V value)Associates the specified value with the specified key in this map.
void putAll(Map map)Copies all of the mappings from the specified map to this map.
V remove(Object key)Removes the mapping for this key from this TreeMap if present.
int size()Returns the number of key value mappings in this map.
NavigableMap subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)Returns a view of the portion of this map whose keys range fromKey to toKey.
SortedMap subMap(K fromKey, K toKey)Returns a view of the portion of this map whose keys range from fromKey, inclusive to toKey, exclusive.
SortedMap tailMap(K fromKey)Returns a view of the portion of this map whose keys are greater than or equal to fromKey.
NavigableMap tailMap(K fromKey, boolean inclusive)Returns a view of the portion of this map whose keys are greater than ( or equal to, if inclusive is true ) fromKey.
Collection values()Returns a Collection view of the values contained in this map.
Methods inherited from class java.util.AbstractMap

equals, hashCode, isEmpty, toString
Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.util.Map

equals, hashCode, isEmpty

conclusion

So this is about treemap in java. I will covering methods in treemap in coming posts.

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Reference – Oracle help centre

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