w3resource

Java Collection, HashSet Exercises: Empty an hash set

Java Collection, HashSet Exercises: Exercise-4 with Solution

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:

Java Collection, ArrayList Exercises: Empty an hash set

Flowchart:

Flowchart: Empty an hash set.

Java Code Editor:

Contribute your code and comments through Disqus.

What is the difficulty level of this exercise?



Java: Tips of the Day

Try and catch:

Java is excellent at catching errors, but it can only recover gracefully if you tell it what to do. The cascading hierarchy of attempting to perform an action in Java starts with try, falls back to catch, and ends with finally. Should the try clause fail, then catch is invoked, and in the end, there's always finally to perform some sensible action regardless of the results. Here's an example:

try {
        cmd = parser.parse(opt, args); 
       
        if(cmd.hasOption("help")) {
                HelpFormatter helper = new HelpFormatter();
                helper.printHelp("Hello ", opt);
                System.exit(0);
                }
        else {
                if(cmd.hasOption("shell") || cmd.hasOption("s")) {
                String target = cmd.getOptionValue("tgt");
                } // else
        } // fi
} catch (ParseException err) {
        System.out.println(err);
        System.exit(1);
        } //catch
        finally {
                new Hello().helloWorld(opt);
        } //finally
} //try

It's a robust system that attempts to avoid irrecoverable errors or, at least, to provide you with the option to give useful feedback to the user. Use it often, and your users will thank you!

Ref: https://red.ht/3EZc9OC