Foreach is a way of traversing a list like for loop and while loop. Variables from outside of Foreach must be final or effective final.
Foreach traversing through a List
public static void foreachWithList() {
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,E
items.forEach(item -> System.out.println(item));
// Output : C
items.forEach(item -> {
if ("C".equals(item)) {
System.out.println(item);
}
});
// method reference
// Output : A,B,C,D,E
items.forEach(System.out::println);
// Stream and filter
// Output : B
items.stream().filter(s -> s.contains("B")).forEach(System.out::println);
}
Foreach traversing through a Map
public static void foreachWithMap() {
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");
}
});
}