In my previous post we have learnt How to Sort HashMap in Java by Keys, in this article we will learn to sort HashMap values. We will be using the below three approaches. Implementing the Comparator Interface along with TreeMap Collection Implementing a separate class implementing Comparator Interface Using Collections.sort() method … [Read more...]
How to Sort HashMap in Java by Keys
We all know that HashMap will not save key-value pairs in any sort of order neither preserve the insertion order. In this tutorial we will learn how to sort a HashMap based on Keys. We will be using two approaches. TreeMap Collection class (Which has in-built support for sorting the elements using Comparable and Comparator Interface) Implementing the Comparator … [Read more...]
Java TreeMap values() Method Example
The values() method of java.util.TreeMap class returns a Collection view of the values contained in this map. The collection's iterator returns the values in ascending order of the corresponding keys. … [Read more...]
Java TreeMap tailMap(K fromKey) Method Example
The tailMap(K fromKey) method of java.util.TreeMap class returns a view of the portion of this map whose keys are greater than or equal to fromKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports. … [Read more...]
Java TreeMap subMap(K fromKey,K toKey) Method Example
The subMap(K fromKey, K toKey) method of java.util.TreeMap class returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports. … [Read more...]
Java TreeMap size() Method Example
The size() method of java.util.TreeMap class returns the number of key-value mappings in this map. … [Read more...]
Java TreeMap remove(Object key) Method Example
The remove(Object key) method of java.util.TreeMap class removes the mapping for this key from this TreeMap if present. … [Read more...]
Java TreeMap putAll(Map map) Method
The put(K key, V value) method of java.util.TreeMap class associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced whereas putAll(Map<? extends K,? extends V> map) copies all of the mappings from the specified map to this map. These mappings replace any mappings that this map had … [Read more...]
Java TreeMap put(K key, V value) Method Example
The put(K key, V value) method of java.util.TreeMap class associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced. … [Read more...]
Java TreeMap pollLastEntry() Method Example
The pollFirstEntry() method of java.util.TreeMap class removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty where as pollLastEntry() method removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty. … [Read more...]
Java TreeMap pollFirstEntry() Method Example
The pollFirstEntry() method of java.util.TreeMap class removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty. … [Read more...]
Java TreeMap navigableKeySet() Method Example
The descendingKeySet() method of java.util.TreeMap class returns a reverse order NavigableSet view of the keys contained in this map. The set's iterator returns the keys in descending order whereas navigableKeySet() returns a NavigableSet view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to … [Read more...]
