Set equals() method in Java with Examples

The equals() method of java.util.Set class is used to verify the equality of an Object with a Set and compare them. The method returns true if the size of both the sets are equal and both contain the same elements.

Syntax:

public boolean equals(Object o)

Parameters: This method takes the object o as a parameter to be compared for equality with this set.

Returns Value: This method returns true if the specified object is equal to this set.

Below are the examples to illustrate the equals() method.

Example 1:

// Java program to demonstrate equals()
// method of Set

import java.util.*;

public class GFG {
    public static void main(String[] argv)
    {

        // Creating object of Set
        Set<String> arrset1 = new HashSet<String>();

        // Populating arrset1
        arrset1.add("A");
        arrset1.add("B");
        arrset1.add("C");
        arrset1.add("D");
        arrset1.add("E");

        // print arrset1
        System.out.println("First Set: "
                           + arrset1);

        // Creating another object of Set
        Set<String> arrset2 = new HashSet<String>();

        // Populating arrset2
        arrset2.add("A");
        arrset2.add("B");
        arrset2.add("C");
        arrset2.add("D");
        arrset2.add("E");

        // print arrset2
        System.out.println("Second Set: "
                           + arrset2);

        // comparing first Set to another
        // using equals() method
        boolean value = arrset1.equals(arrset2);

        // print the value
        System.out.println("Are both set equal? "
                           + value);
    }
}

Output:

First Set: [A, B, C, D, E]
Second Set: [A, B, C, D, E]
Are both set equal? true

Example 2:

// Java program to demonstrate equals()
// method of Set

import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {

        // Creating object of Set
        Set<Integer> arrset1 = new HashSet<Integer>();

        // Populating arrset1
        arrset1.add(10);
        arrset1.add(20);
        arrset1.add(30);
        arrset1.add(40);
        arrset1.add(50);

        // print arrset1
        System.out.println("First Set: " + arrset1);

        // Creating another object of Set
        Set<Integer> arrset2 = new HashSet<Integer>();

        // Populating arrset2
        arrset2.add(10);
        arrset2.add(20);
        arrset2.add(30);

        // print arrset2
        System.out.println("Second Set: " + arrset2);

        // comparing first Set to another
        // using equals() method
        boolean value = arrset1.equals(arrset2);

        // print the value
        System.out.println("Are both set equal? "
                           + value);
    }
}

Output:

First Set: [50, 20, 40, 10, 30]
Second Set: [20, 10, 30]
Are both set equal? false

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Set.html#equals(java.lang.Object)