Gain insights into Java Collections Framework. Delve into lists, sets, and hashmaps. Learn about data modification, sorting, thread-safety, and internal workings for efficient usage.

Collection is one of the most important topics for Java programming. Without the proper knowledge of every collection type in Java, it becomes difficult for you to decide which option to pick in a particular scenario.

This course will give you a great understanding of all collection types available in the Collections Framework like lists, linked lists, sets, and hashmaps. 

After completing this course, you will know how data can be modified within a collection, how to sort a collection, and how it can be made thread-safe. You will also cover the internal working of each Java collection so you can work with them more efficiently.

Collections in Java

# Iteration using `forEach()`

We can use the `forEach(Consumer<? super E> action)` method to iterate over a CopyOnWriteArrayList. This method was added in Java 8 and takes a lambda expression of type Consumer as the parameter.

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

public class CopyOnWriteArrayListDemo {

	public static void main(String args[]) {
		List<String> list = new CopyOnWriteArrayList<>();
		list.add("Apple");
		list.add("Banana");
		list.add("Orange");

		list.forEach(System.out::println);
	}
}


# Iteration using `iterator()`
The `iterator()` method returns an iterator that provides a snapshot of the state of the list when the iterator was constructed. No synchronization is needed while traversing the iterator because the iteration is being done on a snapshot.

If after creating an iterator, an element is added to the ArrayList then `ConcurrentModificationException` is thrown. This is not the case with CopyOnWriteArrayList because the addition of elements takes place on the copy and not the actual array. But the iterator will be able to access only the elements which were present at the time of the creation of the iterator. Let's understand this further through an example.

Let's discuss how we can iterate over a CopyOnWriteArrayList.

Let's Begin

Lists in Java

LinkedList in Java

CopyOnWriteArrayList in Java

Sets in Java

TreeSet in Java

HashMap In Java

TreeMap in Java

LinkedHashMap in Java

Additional Map Implementations

Arrays Class

Collections Class

CopyOnWriteArrayList: Iteration

Iteration using `forEach()`

Iteration using `iterator()`

CopyOnWriteArrayList: Iteration

Iteration using forEach()

Iteration using iterator()

Iteration using `forEach()`

Iteration using `iterator()`