Here’s how to create an ArrayList
, HashSet
, and HashMap
in Java and perform basic operations such as adding, removing, and iterating through them.
1. ArrayList Example
import java.util.ArrayList;
public class ArrayListExample {
public static void main(String[] args) {
// Create an ArrayList
ArrayList<String> fruits = new ArrayList<>();
// Add elements to the ArrayList
fruits.add("Apple");
fruits.add("Banana");
fruits.add("Orange");
// Iterate over the ArrayList
System.out.println("ArrayList Elements:");
for (String fruit : fruits) {
System.out.println(fruit);
}
// Remove an element from the ArrayList
fruits.remove("Banana");
System.out.println("After removing 'Banana': " + fruits);
// Accessing element by index
System.out.println("Element at index 1: " + fruits.get(1));
}
}
2. HashSet Example
import java.util.HashSet;
public class HashSetExample {
public static void main(String[] args) {
// Create a HashSet
HashSet<String> fruits = new HashSet<>();
// Add elements to the HashSet
fruits.add("Apple");
fruits.add("Banana");
fruits.add("Orange");
fruits.add("Apple"); // Duplicate entry (will be ignored)
// Iterate over the HashSet
System.out.println("HashSet Elements:");
for (String fruit : fruits) {
System.out.println(fruit);
}
// Remove an element from the HashSet
fruits.remove("Banana");
System.out.println("After removing 'Banana': " + fruits);
// Check if a value exists
System.out.println("Contains 'Apple'? " + fruits.contains("Apple"));
}
}
3. HashMap Example
import java.util.HashMap;
import java.util.Map;
public class HashMapExample {
public static void main(String[] args) {
// Create a HashMap
HashMap<String, Integer> fruitPrices = new HashMap<>();
// Add key-value pairs to the HashMap
fruitPrices.put("Apple", 100);
fruitPrices.put("Banana", 40);
fruitPrices.put("Orange", 80);
// Iterate over the HashMap
System.out.println("HashMap Elements:");
for (Map.Entry<String, Integer> entry : fruitPrices.entrySet()) {
System.out.println(entry.getKey() + " costs " + entry.getValue() + " units");
}
// Remove an element from the HashMap
fruitPrices.remove("Banana");
System.out.println("After removing 'Banana': " + fruitPrices);
// Check if a key exists
System.out.println("Contains 'Apple'? " + fruitPrices.containsKey("Apple"));
}
}
Key Points:
-
ArrayList:
- Stores elements in the order they are added.
- Allows duplicate elements.
- Provides indexed access to elements.
-
HashSet:
- Does not allow duplicate elements.
- Does not guarantee the order of elements.
-
HashMap:
- Stores key-value pairs.
- Does not allow duplicate keys, but values can be duplicated.
- Efficient for searching, adding, and removing elements using keys.
These examples demonstrate basic operations such as adding, removing, checking existence, and iterating through each data structure.
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