1.1 Normal way to loop a Map.

Map<String, Integer> items = new HashMap<>();items.put("A", 10);items.put("B", 20);items.put("C", 30);items.put("D", 40);items.put("E", 50);items.put("F", 60);for (Map.Entry<String, Integer> entry : items.entrySet()) {System.out.println("Item : " + entry.getKey() + " Count : " + entry.getValue());}

1.2 In Java 8, you can loop a Map with forEach + lambda expression.

Map<String, Integer> items = new HashMap<>();items.put("A", 10);items.put("B", 20);items.put("C", 30);items.put("D", 40);items.put("E", 50);items.put("F", 60);items.forEach((k,v)->System.out.println("Item : " + k + " Count : " + v));items.forEach((k,v)->{System.out.println("Item : " + k + " Count : " + v);if("E".equals(k)){System.out.println("Hello E");}});

2. forEach and List

2.1 Normal for-loop to loop a List.

List<String> items = new ArrayList<>();items.add("A");items.add("B");items.add("C");items.add("D");items.add("E");for(String item : items){System.out.println(item);}

2.2 In Java 8, you can loop a List with forEach + lambda expression or method reference.

List<String> items = new ArrayList<>();items.add("A");items.add("B");items.add("C");items.add("D");items.add("E");//lambda//Output : A,B,C,D,Eitems.forEach(item->System.out.println(item));//Output : Citems.forEach(item->{if("C".equals(item)){System.out.println(item);}});//method reference//Output : A,B,C,D,Eitems.forEach(System.out::println);//Stream and filter//Output : Bitems.stream().filter(s->s.contains("B")).forEach(System.out::println);