AbstractSet Class in Java with Examples

The abstracts class in Java is a part of the Java Collection Framework which implements the Collection interface and extends the AbstractCollection class. It provides a skeletal implementation of the Set interface. This class does not override any of the implementations from the AbstractCollection class, but merely adds implementations for equals() and hashCode() method.

Class Hierarchy:

java.lang.Object
 ? java.util.AbstractCollection<E>
    ? Class AbstractSet<E>

Syntax:

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

Where E is the type of elements maintained by 
this Set.

Constructors in Java AbstractSet:

protected AbstractSet(): The default constructor, but being protected, it doesn’t allow to create an AbstractSet object.

Below is a sample program to illustrate the java AbstractSet:

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// Java code to illustrate AbstractSet

import java.util.*;

public class GFG1 {

public static void main(String[] args) throws Exception

{

try {

// Creating object of AbstractSet<Integer>

AbstractSet<Integer>

abs_set = new TreeSet<Integer>();

// Populating abs_set

abs_set.add(1);

abs_set.add(2);

abs_set.add(3);

abs_set.add(4);

abs_set.add(5);

// print abs_set

System.out.println("AbstractSet: "

+ abs_set);

}

catch (Exception e) {

System.out.println(e);

}

Output:

AbstractSet: [1, 2, 3, 4, 5]

Methods in Java AbstractSet:

equals(Object o): Compares the specified object with this set for equality.
hashCode(): Returns the hash code value for this set.
removeAll(Collection c): Removes from this set all of its elements that are contained in the specified collection (optional operation).

Example:

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// Java code to illustrate

// methods of AbstractSet

import java.util.*;

public class GFG1 {

public static void main(String[] args) throws Exception

{

try {

// Creating object of AbstractSet<Integer>

AbstractSet<Integer>

abs_set = new TreeSet<Integer>();

// Populating abs_set

abs_set.add(1);

abs_set.add(2);

abs_set.add(3);

abs_set.add(4);

abs_set.add(5);

// print abs_set

System.out.println("AbstractSet before "

+ "removeAll() operation : "

+ abs_set);

// Creating another object of ArrayList<Integer>

Collection<Integer>

arrlist2 = new ArrayList<Integer>();

arrlist2.add(1);

arrlist2.add(2);

arrlist2.add(3);

// print arrlist2

System.out.println("Collection Elements"

+ " to be removed : "

+ arrlist2);

// Removing elements from AbstractSet

// specified in arrlist2

// using removeAll() method

abs_set.removeAll(arrlist2);

// print arrlist1

System.out.println("AbstractSet after "

+ "removeAll() operation : "

+ abs_set);

}

catch (NullPointerException e) {

System.out.println("Exception thrown : " + e);

}

Output:

AbstractSet before removeAll() operation : [1, 2, 3, 4, 5]
Collection Elements to be removed : [1, 2, 3]

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AbstractSet Class in Java with Examples

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