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Mastering HashMap in Java: How It Works Internally, Handling Hash Collisions, and Java 8 Improvements

HashMap is one of the most commonly used data structures in Java. It is a part of the Java Collections Framework and is used to store key-value pairs. In this blog post, we will dive into how HashMap works internally, what hash collisions are, and explore some enhancements introduced in Java 8. How HashMap Internally Works At its core, a HashMap uses a data structure called an array to store key-value pairs. Each key is associated with a specific index in the array through a process called hashing. Here's a simplified overview of how it works: Hashing : When you put a key-value pair into a HashMap, the HashMap first calculates a hash code for the key. This hash code is an integer value that represents the key and is used to determine the index where the key-value pair will be stored in the array. Index Calculation : The hash code is then processed to calculate an index within the array. This is typically done by taking the hash code modulo the size of the array. The result is the ...
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Using Java 8 Streams to Find the Second-Highest Salary in an Employee List

To find the second-highest salary from a list of employees using Java 8 streams, you can follow these steps: Create a list of employees with their salaries. Use Java 8 streams to sort the employees by salary in descending order. Skip the first element (which is the employee with the highest salary). Get the first element of the remaining stream (which is the employee with the second-highest salary). Example code: java import java.util.ArrayList; import java.util.List; class Employee { private String name; private double salary; public Employee (String name, double salary) { this .name = name; this .salary = salary; } public double getSalary () { return salary; } } public class SecondHighestSalary { public static void main (String[] args) { List<Employee> employees = new ArrayList <>(); employees.add( new Employee ( "John" , 60000.0 )); employees.add( new Employe...
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Java Data Structures and Algorithms: A Practical Guide with Examples and Top Interview Questions"

Data Structures and Algorithms in Java Understanding Data Structures ArrayList When to Use: Use ArrayList when you need a dynamic array that can grow or shrink in size. It's efficient for random access but less efficient for frequent insertions and deletions. Example Code: java List<String> arrayList = new ArrayList <>(); arrayList.add( "Java" ); arrayList.add( "Data Structures" ); arrayList.add( "Algorithms" ); LinkedList When to Use: LinkedList is suitable for frequent insertions and deletions. It provides better performance than ArrayList in scenarios where elements are frequently added or removed from the middle of the list. Example Code: java LinkedList<String> linkedList = new LinkedList <>(); linkedList.add( "Java" ); linkedList.add( "Data Structures" ); linkedList.add( "Algorithms" ); HashMap When to Use: Use HashMap for fast retrieval of data based on a key. It is efficient for loo...
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Java Collections: From Basics to Advanced Features of 1.7,1.8, 11, 17

Java Collections Framework Overview Concept: The Java Collections Framework provides a unified architecture for handling and manipulating collections of objects. It includes interfaces like List, Set, Map, and their respective implementations, along with algorithms for sorting and searching. Explanation: The framework is designed to be flexible, extensible, and efficient, catering to a wide range of data manipulation needs in Java applications. It simplifies the process of storing, retrieving, and processing data by providing standardized interfaces and implementations. Java 1.7 Concept: Java 1.7 introduced enhancements to the language syntax, focusing on reducing verbosity in code and improving resource management. Explanation: Diamond Operator ( <> ): The diamond operator is a shorthand syntax for specifying generic types, reducing the need to repeat type parameters when instantiating generic classes. Automatic Resource Management (ARM): The try-with-resources statement simpli...
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