Java HashMap Initialization (Load Factor and Initial Capacity)
Learn to initialize Java HashMap object in different ways such as empty map, pre-populated map, and collecting stream elements into the map.
In Java, HashMap is a widely used data structure that belongs to the Java Collections Framework. It is part of the java.util package and provides an efficient way to store and retrieve key-value pairs.
A HashMap allows you to associate keys with values and quickly retrieve values based on their keys.
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Tutorials
Java Map computeIfAbsent()
The Map.computeIfAbsent() method computes the mapped value for a key using a mapping function if the specified key does not exist in the Map or is mapped to a null value. It has been added as the default method in the Map interface in Java 8. 1. When to Use the computeIfAbsent() …
Find Smallest and Largest Value in a Map
Learn to find the minimum value and the maximum value in a Map using Steam API, Collections API and simple comparison using iteration.
Java – Convert a Map to Array, List or Set
Learn to convert Map keys and values to the array, List or Set using the ArrayList and HashSet constructors as well as Stream APIs.
Complete Guide to Java HashMap (with Examples)
The HashMap, part of the Java Collections framework, is used to store key-value pairs for quick and efficient storage and retrieval operations.
Java Map
Maps in Java are the core building blocks of the Collections framework. These tutorials will teach the basics of working with different maps.
Java Nested Map with Examples
A nested Map is Map inside another Map. Learn to create a nested HashMap and add, remove and iterate over the elements with examples.
Clone a HashMap – Shallow and Deep Copy
Learn to create clone of a HashMap in Java. We will see the java programs to create shallow copy and deep copy of a HashMap. 1. Creating a Shallow Copy of Map We can create a shallow copy of a given HashMap in two ways. The first uses the clone() …
Java ConcurrentHashMap vs Collections.synchronizedMap()
Java HashMap is not synchronized by default. Learn to use synchronized maps using Collections.synchronizedMap() and ConcurrentHashMap.
How to Join or Merge Two Maps in Java
Learn merging two hashmaps in both cases – ignoring duplicate keys (overwrites the value) or handling duplicate keys. 1. Merge Two HashMaps Ignoring Duplicate Keys This one is a simple solution. Use firstMap.putAll(secondMap) method that copies all of the mappings from the secondMap to firstMap. As we know hashmap does …
How to Compare Two Maps in Java
Learn to compare two Java Maps for the equality of their entries, key and values, and find the Map differences using Guava’s MapDifference API.
Designing a Good Custom Key for HashMap
Learn to design a good custom key class for HashMap. As a rule, always honor the hashcode and equals contract, and make the class immutable.
Iterate over a HashMap: Performance Comparison
Using the entrySet() specifically is more powerful and yields better performance than using the keySet() for iteration over a HashMap in Java.
Internal Working of HashMap: How HashMap Works?
Learn how hashmap works internally in java with example. Learn the hashmap internal implementation analysis, collision resolution and Java 8 hashmap update.