Lists, sets, and maps in java

In Java, you have several data structures available for storing and manipulating collections of elements, including lists, sets, and maps. Here are examples of how you can use these data structures:

1. Lists: A list is an ordered collection that allows duplicate elements. The most commonly used implementation of the List interface in Java is ArrayList. Here’s an example:

import java.util.ArrayList;
import java.util.List;

public class ListExample {
    public static void main(String[] args) {
        List<String> fruits = new ArrayList<>();

        // Adding elements to the list
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Orange");

        // Accessing elements by index
        String firstFruit = fruits.get(0);
        System.out.println("First fruit: " + firstFruit);

        // Iterating over the list
        for (String fruit : fruits) {
            System.out.println(fruit);
        }
    }
}

Output:

First fruit: Apple
Apple
Banana
Orange

2. Sets: A set is a collection that does not allow duplicate elements. The HashSet implementation is commonly used. Here’s an example:

import java.util.HashSet;
import java.util.Set;

public class SetExample {
    public static void main(String[] args) {
        Set<String> uniqueNames = new HashSet<>();

        // Adding elements to the set
        uniqueNames.add("Alice");
        uniqueNames.add("Bob");
        uniqueNames.add("Alice"); // Duplicate element, won't be added

        // Checking if an element exists in the set
        boolean containsBob = uniqueNames.contains("Bob");
        System.out.println("Set contains Bob: " + containsBob);

        // Iterating over the set
        for (String name : uniqueNames) {
            System.out.println(name);
        }
    }
}

Output:

Set contains Bob: true
Alice
Bob

3. Maps: A map is a collection of key-value pairs, where each key is unique. The HashMap implementation is commonly used. Here’s an example:

import java.util.HashMap;
import java.util.Map;

public class MapExample {
    public static void main(String[] args) {
        Map<String, Integer> wordCount = new HashMap<>();

        // Adding elements to the map
        wordCount.put("apple", 3);
        wordCount.put("banana", 2);
        wordCount.put("orange", 5);

        // Accessing values by key
        int count = wordCount.get("banana");
        System.out.println("Count of banana: " + count);

        // Iterating over the map
        for (Map.Entry<String, Integer> entry : wordCount.entrySet()) {
            String word = entry.getKey();
            int value = entry.getValue();
            System.out.println(word + ": " + value);
        }
    }
}

Output:

Count of banana: 2
apple: 3
banana: 2
orange: 5

These examples demonstrate the basic usage of lists, sets, and maps in Java. There are additional methods and features available for each data structure, so make sure to consult the Java documentation for more information.