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How to iterate the contents of a collection using forEach() in Java?
Lambda expression is the anonymous representation of a function descriptor of a functional interface. As we know that all collection interfaces like List, Set and Queue use an Iterable as their super interface. Since Java 8, an Iterable interface introduces a new method called forEach(). This method performs an action on the contents of Iterable in the order elements that occur when iterating until all elements have processed.
Syntax
void forEach(Consumer<? Super T> action)
In the below program, we can iterate the contents of a list using the forEach() method and print the contents by using lambda expression and static method reference.
Example
import java.util.*;
import java.util.function.*;
public class LambdaMethodRefIterationTest {
public static void main(String[] args) {
List<String> countries = Arrays.asList("India", "Australia", "England", "Newzealand", "Scotland");
System.out.println("==== Iterating by passing Lambda Expression ====");
countries.forEach(s -> System.out.println(s));
System.out.println("
==== Iterating by passing Static Method Reference ====");
countries.forEach(System.out::println);
System.out.println("
==== Iterating by passing Static Method Reference ====");
countries.forEach(Country::countWord);
}
}
class Country {
static void countWord(String s) {
System.out.println(s.length());
}
}Output
==== Iterating by passing Lambda Expression ==== India Australia England Newzealand Scotland ==== Iterating by passing Static Method Reference ==== India Australia England Newzealand Scotland ==== Iterating by passing Static Method Reference ==== 5 9 7 10 8
Updated on: 13-Jul-2020
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