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

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);});