Java: Compare two sets and retain elements which are same on both sets

Last update on May 22 2025 13:15:47 (UTC/GMT +8 hours)

11. Retain Common Elements in Sets

Write a Java program to compare two sets and retain elements that are the same.

Sample Solution:

Java Code:

import java.util.*;
  public class Exercise11 {
  public static void main(String[] args) {
     // Create a empty hash set
        HashSet<String> h_set1 = new HashSet<String>();
     // use add() method to add values in the hash set
          h_set1.add("Red");
          h_set1.add("Green");
          h_set1.add("Black");
          h_set1.add("White");
          System.out.println("Frist HashSet content: "+h_set1);
          HashSet<String>h_set2 = new HashSet<String>();
          h_set2.add("Red");
          h_set2.add("Pink");
          h_set2.add("Black");
          h_set2.add("Orange");
          System.out.println("Second HashSet content: "+h_set2);
          h_set1.retainAll(h_set2);
          System.out.println("HashSet content:");
          System.out.println(h_set1);
     }
}

Sample Output:

Frist HashSet content: [Red, White, Black, Green]                      
Second HashSet content: [Red, Pink, Black, Orange]                     
HashSet content:                                                       
[Red, Black]

Pictorial Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to compute the intersection of two sets using the retainAll() method.
• Write a Java program to use Java streams to find common elements between two sets and collect them into a new set.
• Write a Java program to compare two sets and then remove all elements from one that are not present in the other.
• Write a Java program to implement a custom method that returns the intersection of two sets without using built-in collection methods.

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