Set Intersection in Java

In Java, Sets. intersection () method of Guava returns a non-modifiable view of the intersection of provided two sets. All the elements or values which are present in both sets will be returned. The order of iteration of both returned and first set will be similar.

Syntax:

public static <E>
Sets.SetView<E>
intersection(Set<E> set1, Set<?> set2)

Return Value: The above-mentioned method will return a non-modifiable view of the two sets, respectively.

Let us understand about Set Intersection in detail with the help of few Java example programs.

Example 1:

Filename: Example1.java

// Java program for demonstration of Guava's Sets.intersection() method.
import java.util.HashSet;
import java.util.Set;
public class GuavaSets {
public static void main(String[] args) {
// Creation of Set objects.
Set<Integer> first_set = new HashSet<>();
Set<Integer> second_set = new HashSet<>();

// Assigning values to the first set.
first_set.add(1);
first_set.add(2);
first_set.add(3);

// Assigning values to the second set.
second_set.add(2);
second_set.add(3);
second_set.add(4);
System.out.println("First Set: " + first_set);
System.out.println("Second Set: " + second_set);
// Calculating the Intersection of first and Second Sets
first_set.retainAll(second_set);
// Printing the intersection of the first and second sets.
System.out.println("Intersection of Set 1 and Set 2: " + first_set);
}
}

Output:

First Set: [1, 2, 3]
Second Set: [2, 3, 4]
Intersection of Set 1 and Set 2: [2, 3]

Explanation:

In the above-mentioned Java example program, two sets of Integer data types are declared. The first set contains a few integer values in it. Similarly, the second set stores a few integer values in it. Using the retainAll() method, we are storing the intersection of both first and second set in the first set respectively. The result will be the values which are common in both first and second set. The result is being printed.

Example 2:

Filename: Example1.java

// Java program for demonstration of Guava's Sets.intersection() method.
import java.util.HashSet;
import java.util.Set;
public class GuavaSets1 {
public static void main(String[] args) {
// Creation of Set objects.
Set<Character> first_set = new HashSet<>();
Set<Character> second_set = new HashSet<>();

// Assigning values to the first set.
first_set.add('a');
first_set.add('b');
first_set.add('c');

// Assigning values to the second set.
second_set.add('b');
second_set.add('e');
second_set.add('z');
System.out.println("First Set: " + first_set);
System.out.println("Second Set: " + second_set);
// Calculating the Intersection of first and Second Sets
first_set.retainAll(second_set);
// Printing the intersection of the first and second sets.
System.out.println("Intersection of Set 1 and Set 2: " + first_set);
}
}

Output:

First Set: [a, b, c]
Second Set: [b, e, z]
Intersection of Set 1 and Set 2: [b]

Explanation:

In the above-mentioned Java example program, two sets of Character data types are declared. The first set contains few Character values in it. Similarly, the second set stores few Character values in it. Using the retainAll() method, we are storing the intersection of both first and second set in the first set respectively. The result obtained will be the values or elements common in both first and second set. The result obtained is being printed.

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