why is my hashmap printing only "}" java code example

Example 1: how to print the map in java

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.stream.Stream;
 
class MapUtil
{
    // Program to print all keys present in the Map using keySet() in Java
    public static void main (String[] args)
    {
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "One");
        map.put(2, "Two");
 
        // 1. using Iterator
        Iterator<Integer> itr = map.keySet().iterator();
        while (itr.hasNext()) {
            System.out.println(itr.next());
        }
 
        // 2. For-each Loop
        for (Integer key : map.keySet()) {
            System.out.println(key);
        }
 
        // 3. Java 8 - Collection.iterator() + Iterator.forEachRemaining()
        map.keySet().iterator()
                .forEachRemaining(System.out::println);
 
        // 4. Java 8 - Collection.stream() + Stream.forEach()
        map.keySet().stream()
                .forEach(System.out::println);
 
        // Java 8 - Stream.of() + Collection.toArray() + Stream.forEach()
        Stream.of(map.keySet().toArray())
                .forEach(System.out::println);
 
        // 5. Convert to String
        System.out.println(map.keySet().toString());
 
        // Java 8
        Stream.of(map.keySet().toString())
                .forEach(System.out::println);
    }
}

Example 2: print only values in map

map.forEach((key, value) -> System.out.println(key + " " + value));