Java: Test a hash set is empty or not

Last update on May 22 2025 13:15:50 (UTC/GMT +8 hours)

5. Check if HashSet is Empty

Write a Java program to test if a hash set is empty or not.

Sample Solution:

Java Code:

import java.util.*;

  public class Exercise5 {
  public static void main(String[] args) {
         // Create a empty hash set
     HashSet<String> h_set = new HashSet();
   // use add() method to add values in the hash set
          h_set.add("Red");
          h_set.add("Green");
          h_set.add("Black");
          h_set.add("White");
          h_set.add("Pink");
          h_set.add("Yellow");
    System.out.println("Original Hash Set: " + h_set);
    System.out.println("Checking the above array list is empty or not! "+h_set.isEmpty());
    System.out.println("Remove all the elements from a Hash Set: ");
    h_set.removeAll(h_set);
    System.out.println("Hash Set after removing all the elements "+h_set);   
   }
}

Sample Output:

Original Hash Set: [Red, White, Pink, Yellow, Black, Green]            
Checking the above array list is empty or not! false                   
Remove all the elements from a Hash Set:                               
Hash Set after removing all the elements [] 

Pictorial Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to check whether a HashSet is empty using the isEmpty() method and print an appropriate message.
• Write a Java program to compare a HashSet’s size to zero as an alternative check for emptiness.
• Write a Java program to use a lambda expression with allMatch() on a stream derived from the HashSet to determine emptiness.
• Write a Java program to test a HashSet's emptiness after bulk removal operations and log the results.

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