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The Java HashMap Under the Hood 1. Overview In this article, we are going to explore the most popular implementation of Map interface from the Java Collections Framework in more detail, picking up where our intro article left off. Before we get started with the implementation, it’s important to point… Continue Reading java-hashmap-advanced
Java TreeMap vs HashMap 1. Introduction In this article, we’re going to compare two Map implementations: TreeMap and HashMap. Both implementations form an integral part of the Java Collections Framework and store data as key-value pairs. 2. Differences ==== 2.1. Implementation We’ll first talk about the HashMap which is a… Continue Reading java-treemap-vs-hashmap
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A Guide to EnumMap 1. Overview EnumMap is a Map implementation that exclusively takes Enum as its keys. In this tutorial, we’ll discuss its properties, common use cases and when we should use it. 2. Project Setup Imagine a simple requirement where we need to map days of the week with the sport we… Continue Reading java-enum-map
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How to Convert List to Map in Java 1. Overview Converting List to Map is a common task. In this tutorial, we’ll cover several ways to do this. We’ll assume that each element of the List has an identifier which will be used as a key in the resulting Map. 2.… Continue Reading java-list-to-map
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An Introduction to Java.util.Hashtable Class 1. Overview Hashtable is the oldest implementation of a hash table data structure in Java. The HashMap is the second implementation, which was introduced in JDK 1.2. Both classes provide similar functionality, but there are also small differences, which we’ll explore in this tutorial. 2. When to use Hashtable… Continue Reading java-hash-table
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Guide to Guava Multimap 1. Overview In this article, we will look at one of Map implementations from Google Guava library – Multimap. It is a collection that maps keys to values, similar to java.util.Map, but in which each key may be associated with multiple values. 2. Maven Dependency First,… Continue Reading guava-multimap
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Merging Two Maps with Java 8 1. Introduction In this quick tutorial, we’ll demonstrate how to merge two maps using the Java 8 capabilities. To be more specific, we’ll examine different merging scenarios including maps having duplicate entries. 2. Initialization As a start, let’s define two Map instances: private static… Continue Reading java-merge-maps
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Map of Primitives in Java 1. Overview In this tutorial, we’ll learn how to construct a map with primitive keys and values. As we know, the core Java Maps don’t allow storage of primitive keys or values. That’s why we’ll introduce a number of external third-party libraries which provide primitive… Continue Reading java-map-primitives
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Apache Commons Collections BidiMap 1. Overview In this short article, we’ll be looking at an interesting data structure in the Apache Commons Collections library – the BidiMap. The BidiMap adds a possibility of looking up the key using the corresponding value on top of the standard Map interface. 2. Dependencies… Continue Reading commons-collections-bidi-map
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Apache Commons Collections MapUtils 1. Introduction MapUtils is one of the tools available in the Apache Commons Collections project. Simply put, it provides utility methods and decorators to work with java.util.Map and java.util.SortedMap instances. 2. Setup Let’s start by adding the dependency: <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-collections4</artifactId> <version>4.1</version> </dependency> 3. Utility Methods… Continue Reading apache-commons-map-utils
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