In this quick article, we’ll take a look athow to invert aMapin Java. The idea is to create a new instance ofMap<V, K>for a given map of typeMap<K, V>. In addition, we’ll also see how to handle the case where there are duplicate values present in the source map. Please r...
HashMapis a very powerful data structure inJava. We use it everyday and almost in all applications. There are quite a few examples which I have written before onHow to Implement Threadsafe cache, How to convertHashmap to Arraylist? We used Hashmap in both above examples but those are pret...
// Declares String reference variable str1 and str2 String str1; String str2; // Assigns the reference of a String object "Hello" to str1 str1 = new String( "Hello World !!" ); // Assigns the reference stored in str1 to str2 str2 = str1; System.out.println( str1 ); //Hel...
HashMap class is serialized by default which means we need not to implement Serializable interface in order to make it eligible for Serialization. In this tutorial we will learnHow to write HashMap object and it’s content into a fileandHow to read the HashMap object from the file.Before I...
Here’s how to implement it: importjava.util.HashMap;importjava.util.Map;publicclassMain{publicstaticvoidmain(String[]args){HashMap<String,Integer>map=newHashMap<>();map.put("One",1);map.put("Two",2);map.put("Three",3);for(Map.Entry<String,Integer>entry:map.entrySet()){String key...
2. Comparing Map Keys We can compare two Maps to have the same keys or not. Or we can find the missing keys in the second Map, if needed. 2.1. Both Maps Have Same Keys If we want tocompare hashmaps by keysi.e. two hashmaps will be equal if they have the exactly the same set...
There are differences in languages like Java and Python (for example, in Java, you can use the HashMap interface as a part of the Java collection package). Still, ultimately, most general-purpose languages have a few different ways to implement a hash table. Let's start with the simplest...
2. Command Design Pattern in Java - Example Below is our sample program to demonstrate how to use the command pattern in Java. This class represents the client side of the command pattern Client.java importjava.util.HashMap;importjava.util.Map;importorg.slf4j.Logger;importorg.slf4j.LoggerFact...
When writing complex data processes, we often find hash tables very useful. But when you decide to use your object as a key, it’s easy to implement it the wrong way. A little disclaimer: this article requires some specific knowledge of Java development, and I can’t cover all this ...
In this tutorial, we’ll explore how to sort aLinkedHashMapby values in Java. 2. Sorting by Value The default behavior of aLinkedHashMapis to maintain the order of elements based on the insertion order. This is useful in cases where we want to keep track of the sequence in which eleme...