Difference between Collection.stream().forEach() and Collection.forEach() in Java

Collection.stream().forEach() and Collection.forEach() both are used to iterate over collection. 

Collection.forEach()  uses the collection’s iterator. Most of the collections doesn’t allow the structurally modification while iterating over them. If any element add or remove while iteration they will immediately throw concurrent modification exception. If Collection.forEach() is iterating over the synchronized collection then they will lock the segment of the collection and hold it across all the calls. 

Collection.stream().forEach() is also used for iterating the collection but it first convert the collection to the stream and then iterate over the stream of the collection therefore the processing order is undefined. It also throws the concurrent modification exception, if any structural changes happened while iterating over them it will throw an exception immediately.

Example Collection.stream().forEach

import java.util.ArrayList;
import java.util.List;
public class Main {
   public static void main(String[] args) {
      List list= new ArrayList();
      list.add("Ram");
      list.add("TutorialPoints");
      list.stream().forEach(System.out::print);
   }
}

Example Collection.forEach

import java.util.ArrayList;
import java.util.List;
public class Main {
   public static void main(String[] args) {
      List list= new ArrayList();
      list.add("Ram");
      list.add("TutorialPoints");
      list.forEach(System.out::print);
   }
}