Iteration

Iteration in Java refers to the process of iterating or traversing through a collection (such as a List, Set, or Map) to access its elements. Iteration is a crucial aspect of working with collections in Java and can be performed using various techniques like for, while, do-while loops, and using the Iterator interface.

Iterating Over Collections Using Different Methods

  1. Using For-each Loop:

    • The simplest and most concise method of iterating over collections.
    List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
for (String name : names) {
    System.out.println(name);
}


2. **Using Iterator**:

   * The `Iterator` interface provides methods like `hasNext()` and `next()` to iterate through the elements in a collection.

   ```java
   Iterator<String> iterator = names.iterator();
   while (iterator.hasNext()) {
       System.out.println(iterator.next());
   }

  1. Using forEach Method (Java 8+):

    • Java 8 introduced the forEach() method that allows iterating over collections in a functional style.
    names.forEach(name -> System.out.println(name));

  2. Using ListIterator (For Lists):

    • ListIterator is specifically used for iterating over List objects and provides additional methods like add(), set(), and bi-directional iteration.
    ListIterator<String> listIterator = names.listIterator();
while (listIterator.hasNext()) {
    System.out.println(listIterator.next());
}

Benefits of Iteration

  • Simplifies Data Access: Iteration provides an easy and consistent way to access and process elements in a collection.

  • Flexibility: Different iteration techniques cater to specific needs such as traversing a collection in reverse order, modifying elements during iteration, or performing actions on each element.

  • Functional Programming: With Java 8+, iteration can be performed using lambda expressions and streams, enabling a more declarative style of coding.

Example: Iterating Through a Set

import java.util.*;

public class IterationExample {
    public static void main(String[] args) {
        Set<String> names = new HashSet<>(Arrays.asList("Alice", "Bob", "Charlie"));

        // Using Iterator
        Iterator<String> iterator = names.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }
}

🔗 Related Notes