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Java Collection, HashMap Exercises: Check whether a map contains key-value mappings (empty) or not

Java Collection, HashMap Exercises: Exercise-5 with Solution

Write a Java program to check whether a map contains key-value mappings (empty) or not.

Sample Solution:-

Java Code:

import java.util.*;  
public class Example5 {  
   public static void main(String args[]) {
  HashMap <Integer,String> hash_map = new HashMap <Integer,String> ();
  hash_map.put(1, "Red");
  hash_map.put(2, "Green");
  hash_map.put(3, "Black");
  hash_map.put(4, "White");
  hash_map.put(5, "Blue");
  // check if map is empty
  boolean result = hash_map.isEmpty();
  // check the result
  System.out.println("Is hash map empty: " + result);
  // Removing all the elements from the linked map
  hash_map.clear();
  // check if map is empty
  result = hash_map.isEmpty();
  // check the result
  System.out.println("Is hash map empty: " + result);
 }
}

Sample Output:

Is hash map empty: false                                               
Is hash map empty: true

Java Code Editor:

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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