Java: Empty an hash set

Last update on May 22 2025 13:14:32 (UTC/GMT +8 hours)

4. Clear HashSet

Write a Java program to empty an hash set.

Sample Solution:

Java Code:

import java.util.*;

  public class Exercise4 {
  public static void main(String[] args) {
         // Create a empty hash set
     HashSet<String> h_set = new HashSet<String>();
   // 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);
    // Remove all elements
    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]            
Hash Set after removing all the elements [] 

Pictorial Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to clear a HashSet using the clear() method and then verify its emptiness with isEmpty().
• Write a Java program to remove all elements from a HashSet by iterating through it and then print the final size.
• Write a Java program to use Java streams to filter out all elements from a HashSet and collect the result into a new, empty set.
• Write a Java program to simulate clearing a HashSet by reassigning it to a new instance and then checking if it is empty.

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