AbstractSet Class in Java

In Java, the AbstractSet class is part of the Java Collections Framework. It provides a Skeleton implementation of the set interface, which is a collection that does not allow duplicate elements. This class is abstract, meaning it cannot be instantiated directly, but it can be extended to create a custom set implementation

• AbstractSet implements the set interface but does not provide a full implementation of all set methods.
• It provides implementations for methods like size(), isEmpty() and contains()
• It requires subclasses to implement the iterator()method to define how elements are iterated over

Example: This example demonstrates how to insert elements into a set and print them.

Elements in the set:
20
10
30

AbstractSet Class Hierarchy

From the below diagram, it can be concluded that it implements Iterable<E>, Collection<E>, Set<E> interfaces. The direct subclasses are CopyOnWriteArraySet, EnumSet, HashSet, TreeSet.

👁 AbstractSet-Class-in-Java

Declaration of AbstractSet Class

In Java, the declaration of AbstractSet Class can be done as:

public abstract class AbstractSet<E> extends AbstractCollection<E> implements Set<E>

Constructor

Example: This example demonstrates how a protected constructor in an abstract class can only be called by its subclasses, and how the subclass must implement abstract methods from the abstract class.

AbstractSet constructor called
MySet constructor called
Displaying elements in MySet

Performing Various Operations on AbstractSet

1. Adding elements: We can use add() method to insert element to a AbstractSet class.

Example: This example demonstrates how to insert elements into an AbstractSet using a LinkedHashSet to maintain the order of insertion and display them in that order.

AbstractSet elements: [10, 20, 30, 40, 50]

2. Removing Elements: We can use various methods like remove(), removeAll(), retainAll() and clear() method to remove elements from the AbstractSet.

Example: This example demonstrates how to remove a single element using remove() and multiple elements using removeAll() from a HashSet, which a concrete subclass of AbstractSet.

Set before removal(): [1, 2, 3, 4, 5]
Set after removal of element 3: [1, 2, 4, 5]
Set after removeAll() : [2, 4]

3. Iterating Elements: We can use the iterator() method to iterate over the elements of a AbstractSet.

Example:

Iterating over the set elements:
1 2 3 4 5 

Methods

Methods Declared in Class java.util.AbstractCollection

Methods Declared in Interface java.util.Collection

Methods Declared in interface java.lang.Iterable

Methods Declared in interface java.util.Set

Characteristics

Some of the key characteristics of AbstractSet are listed below:

• Implements the Set interface: AbstractSet implements the Set interface, which means that it provides a standard set of methods to manipulate sets.
• Implements some set methods: AbstractSet implements some of the methods of the Set interface, such as size(), isEmpty(), contains(), and remove().
• Supports iterator: AbstractSet provides an iterator method that returns an Iterator over the elements in the set.
• Does not implement all set methods: AbstractSet is an abstract class and does not implement all the methods of the Set interface. Some of the methods that are not implemented include add(), addAll(), and clear(). These methods must be implemented by subclasses of AbstractSet.
• Provides default implementations: AbstractSet provides default implementations for some methods of the Set interface, which can be overridden by subclasses if needed.
• Supports null elements: AbstractSet allows null elements to be added to the set.
• Unordered: AbstractSet is an unordered set, which means that the order in which elements are added to the set is not preserved.
• Thread-unsafe: AbstractSet is not thread-safe, which means that if multiple threads access the same set simultaneously, it can lead to data inconsistencies. If thread safety is required, a synchronized set or a concurrent set can be used.