Curriculum
HashMap and HashSet Introduction in Java is an important topic in the Java Collections Framework used for storing and managing data efficiently. HashMap stores key-value pairs, while HashSet stores unique elements without duplicates.
In this Core Java course in Jaipur, students will learn HashMap in Java, HashSet in Java, hashing concepts, key-value mapping, unique collections, and practical examples used in software development.
HashMap and HashSet are widely used in:
Understanding HashMap and HashSet introduction in Java helps students build scalable and high-performance applications.
Hashing is a technique used to:
Hashing improves:
HashMapis a collection class used to:
Each key in HashMap:
while:
HashMap provides:
import java.util.HashMap;HashMap<KeyType, ValueType> mapName =
new HashMap<>();import java.util.HashMap;
class HashMapExample {
public static void main(String[] args) {
HashMap<Integer, String> students =
new HashMap<>();
students.put(1, "Rahul");
students.put(2, "Aman");
students.put(3, "Priya");
System.out.println(students);
}
}{1=Rahul, 2=Aman, 3=Priya}Important methods:
put()adds key-value pair.
students.put(1, "Rahul");get()retrieves value using key.
System.out.println(students.get(1));Rahulremove()deletes element using key.
students.remove(2);Checks whether key exists.
students.containsKey(1);import java.util.HashMap;
class MapLoop {
public static void main(String[] args) {
HashMap<Integer, String> students =
new HashMap<>();
students.put(1, "Rahul");
students.put(2, "Aman");
for(Integer key : students.keySet()) {
System.out.println(key + " " +
students.get(key));
}
}
}1 Rahul
2 AmanHashSetis a collection class used to:
Duplicate values are automatically removed.
HashSet provides:
import java.util.HashSet;HashSet<dataType> setName =
new HashSet<>();import java.util.HashSet;
class HashSetExample {
public static void main(String[] args) {
HashSet<String> languages =
new HashSet<>();
languages.add("Java");
languages.add("Python");
languages.add("Java");
System.out.println(languages);
}
}[Java, Python]Duplicate value:
Javais automatically removed.
Important methods:
Checks whether element exists.
languages.contains("Java");import java.util.HashSet;
class SetLoop {
public static void main(String[] args) {
HashSet<Integer> numbers =
new HashSet<>();
numbers.add(10);
numbers.add(20);
for(Integer value : numbers) {
System.out.println(value);
}
}
}| HashMap | HashSet |
|---|---|
| Stores key-value pairs | Stores unique values |
| Uses put() method | Uses add() method |
| Keys must be unique | Elements must be unique |
| HashMap | ArrayList |
|---|---|
| Uses key-value pairs | Uses indexes |
| Faster searching | Sequential access |
HashMap internally uses:
for faster data storage and retrieval.
HashMap stores:
HashMap manages:
HashMap processes:
HashSet stores:
HashSet removes:
HashSet manages:
These collections provide:
These collections do not guarantee insertion order.
Duplicate keys overwrite previous values.
Incorrect:
HashMap map = new HashMap();Understanding these collections helps students:
In this lesson, students learned:
These concepts are essential for Java programming, backend development, and enterprise software systems.
HashMap stores key-value pairs with unique keys.
HashSet stores unique elements without duplicates.
No, HashMap allows only unique keys.
No, HashSet does not guarantee insertion order.
They use hashing techniques for faster data access.
They are used in banking systems, APIs, login systems, and enterprise applications.