Java – Map & BiConsumer Function Lambda Expression Example

This article represents code samples representing lambda expression and the related ease with which one could print key and value of a Map object using one liner. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.
Code Sample – Printing Map using BiConsumer Functional Interface

Following is detail for Map.forEach API in Java 8. Read further on this page.

		default void forEach(BiConsumer<? super K,? super V> action)
		Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. Unless otherwise specified by the	implementing class, actions are performed in the order of entry set iteration (if an iteration order is specified.) Exceptions thrown by the action are relayed to the caller.

Pay attention to following:

  • Traditional way of printing key & value would require one to get an iterator of Map.Entry objects and print key and values
  • Lambda expression way represents defining a BiConsumer implementation by passing two input arguments as key and value of Map and printing their values.
	public static void main(String[] args) {
		Map<String, String> map = new HashMap<String, String>();
		String[][] tempStrArr = {{"Chris","USA"}, {"Raju","India"}, {"Lynda","Canada"} };
		// Create a Map using String Array
		for( int i = 0; i < tempStrArr.length; i++ ) {
			map.put( tempStrArr[i][0], tempStrArr[i][1] );
		// Traditional way of printing key, value
		Iterator<Map.Entry<String, String>> iter = map.entrySet().iterator();
		if( iter != null ) {
			while( iter.hasNext() ) {
				Map.Entry<String, String> entry =;
				System.out.println( "Key: " + entry.getKey() + "\t" + " Value: " + entry.getValue() );
		// Using Lambda Expression: All in One line
		map.forEach( (key, value) -> { System.out.println( "Key: " + key + "\t" + " Value: " + value ); });


Ajitesh Kumar
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Ajitesh Kumar

I have been recently working in the area of Data Science and Machine Learning / Deep Learning. In addition, I am also passionate about various different technologies including programming languages such as Java/JEE, Javascript, Python, R, Julia etc and technologies such as Blockchain, mobile computing, cloud-native technologies, application security, cloud computing platforms, big data etc. I would love to connect with you on Linkedin and Twitter.
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