The map is a set of key-value mappings. The keys are unique.
HashMap class is a hash table based implementation of the Map:
1. Does not maintain any order.
2. Allows one null as a key and any number of null as a value.
3. Unsynchronized.
Hashtable. This class implements a hash table, which maps keys to values. Any non-null an object can be used as a key or as a value:
1. Does not maintain any order.
2. Does not allow null as key and value.
3. Synchronized.
LinkedHashMap class is a hash table and linked list based implementation of the Map interface. The difference from HashMap is that it maintains a doubly-linked list to provide insertion(iteration) order. Note that insertion order is not affected if a key is re-inserted into the map.
TreeMap class — Red-Black tree based NavigableMap implementation. The map is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time, depending on which constructor is used.
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OS, File, and File System
Working with terminal
Welcome to Java Programming Language
Variables and Primitives in Java
Convert String to numeric data type
Input from the terminal in Java
Methods with Java
Java Math Operators and special operators
Conditional branching in Java
Switch statement in Java
Ternary operator in Java
Enum in Java
String class and its methods in Java
Loops in Java
Access modifiers in Java
Static keyword in Java
The final keyword in Java
Class and Object in Java
Object-Oriented Programming in Java
OOP: Encapsulation in Java
OOP: Inheritance in Java
OOP: Abstraction in Java
OOP: Polymorphism in Java
The method Overriding vs Overloading in Java
Array in Java
Data Structures with Java
Collection framework in Java
ArrayList in Java
Set in Java
Map in Java
Date and Time in Java
Exception in Java
How to work with files in Java
Design Patterns
Generics in Java
Multithreading in java
Annotations in Java
Reflection in Java
Reflection & Annotations - The Powerful Combination
Run terminal commands from Java
Lambda in Java
Unit Testing in Java
Big O Notation for coding interviews
Top Java coding interview questions for SDET
