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Java – Map & BiConsumer Function Lambda Expression Example

· Java Zone

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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 = iter.next();
				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 ); });

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Published at DZone with permission of Ajitesh Kumar, DZone MVB. See the original article here.

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