Java: Convert a hash set to a List/ArrayList

Last update on May 22 2025 13:14:30 (UTC/GMT +8 hours)

9. Find Elements Less Than 7 in TreeSet

Write a Java program to convert a hash set to a List/ArrayList.

Sample Solution:

Java Code:

import java.util.*;

  public class Exercise9 {
  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);
    
    // Create a List from HashSet elements
     List<String> list = new ArrayList<String>(h_set);
 
     // Display ArrayList elements
     System.out.println("ArrayList contains: "+ list);
  }
}

Sample Output:

Original Hash Set: [Red, White, Pink, Yellow, Black, Green]            
ArrayList contains: [Red, White, Pink, Yellow, Black, Green]

Pictorial Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to use headSet() on a TreeSet to extract all numbers less than 7.
• Write a Java program to iterate through a TreeSet and print only those numbers below a given threshold.
• Write a Java program to filter a TreeSet using Java streams to collect numbers less than 7 into a new set.
• Write a Java program to remove all numbers greater than or equal to 7 from a TreeSet and display the remaining elements.

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