Printing key value pairs with given string format e.g. "%s is key of %s"

PrintableHashMap.java

package com.example.collection;

import java.util.HashMap;
import java.util.Iterator;

public class PrintableHashMap<K, V> extends HashMap<K, V> {

	private static final long serialVersionUID = 1L;

	public String toString(String format) {
		Iterator<Entry<K, V>> iterator = entrySet().iterator();
		if (!iterator.hasNext()) {
			return "{}";
		}

		StringBuilder sb = new StringBuilder();
		sb.append("[");
		while (iterator.hasNext()) {
			Entry<K, V> entry = iterator.next();
			K key = entry.getKey();
			V value = entry.getValue();

			String keyString = key == this ? "(this Map)" : key.toString();
			String valueString = value == this ? "(this Map)" : value.toString();

			String outputItem = String.format(format, keyString, valueString);
			sb.append(outputItem);
			if (!iterator.hasNext())
				break;
			sb.append(',').append(' ');
		}
		return sb.append(']').toString();
	}

	public static void main(String[] args) {
		PrintableHashMap<String, String> map = new PrintableHashMap<>();
		map.put("BJK", "Besiktas");
		map.put("FB", "Fenerbahce");
		map.put("GS", "Galatasaray");
		System.out.println(map.toString("%s is abbr of %s"));
	}
}

OUTPUT:
[BJK is abbr of Besiktas, FB is abbr of Fenerbahce, GS is abbr of Galatasaray]