Java – One-Liner Lambda Expression to Print Map/List Objects

This article represents code samples to print element of collections such as Map and List/Set using lambda expression. I just love it as it has made life so simpler by helping me achieve this using just one line of code. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.

Following are the key points described later in this article:

• Print Map key-Value Pair using Lambda Expression
• Print List value using Lambda Expression

Print Map key-Value Pair using Lambda Expression

Pay attention to forEach function that takes a reference to BiConsumer function interface and prints the key and value. This is so easy against the traditional way of getting an iterator of Map.Entry objects and print key and value for each Map.Entry object.

  
// Create a Map using String Array
Map<String, String> map = new HashMap<String, String>();
String[][] mapArr = {{"Chris","USA"}, {"Raju","India"}, {"Lynda","Canada"} };
for( int i = 0; i < mapArr.length; i++ ) {    
     map.put( mapArr[i][0], mapArr[i][1] );   
}
//
// Print the key and value of Map using Lambda expression   
//   
map.forEach((key, value) -> {System.out.println( "Key: " + key + " - Value:" + value);});

Print List value using Lambda Expression

Pay attention to forEach function that takes a reference to a Consumer function and prints each value. This is so easy against the traditional way of getting an instance of iterator and then print value by retrieving each element from iterator.

  
// Create a list from a String array
List list = new ArrayList();
String[] strArr = { "Chris", "Raju", "Jacky" };
for( int i = 0; i < strArr.length; i++ ) {    
list.add( strArr[i] );   
}     
//   
// Print the key and value of Map using Lambda expression   
//   
list.forEach((value) -> {System.out.println( "Value:" + value);});