Java8中的forEach使用及说明

default void forEach(Consumer<? super T> action) {  
 Objects.requireNonNull(action);                        
 for (T t : this) {        
     action.accept(t);    
 } 
}

Consumer<Object> action = new Consumer<Object>()
{
    @Override
    public void accept(Object t)
    {
        //perform action
    }
};

ArrayList<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
Consumer<Integer> action = System.out::println;
list.stream().filter(n -> n % 2 == 0).forEach(action);

ArrayList<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
Consumer<Integer> action = System.out::println;
list.forEach(action);

    HashMap<String, Integer> map = new HashMap<>();
    map.put("A", 1);
    map.put("B", 2);
    map.put("C", 3);
    // 1.Map entries
    Consumer<Map.Entry<String, Integer>> action = System.out::println;
    map.entrySet().forEach(action);
    // 2.Map keys
    Consumer<String> actionKeys = System.out::println;
    map.keySet().forEach(actionKeys);
    // 3. Map values
    Consumer<Integer> actionValues = System.out::println;    
    map.values().forEach(actionValues);

    HashMap<String, Integer> map = new HashMap<>();
    map.put("A", 1);
    map.put("B", 2);
    map.put("C", 3);
    // 1.Map entries
    Consumer<Map.Entry<String, Integer>> action = entry -> {
        System.out.println("Key is " + entry.getKey());
        System.out.println("Value is " + entry.getValue());
        System.out.println();
    };
    map.entrySet().forEach(action);

  List<String> list = Arrays.asList("12", "14345", "16", "abch", "sdfhrthj", "mvkd");
        list.stream().forEach(e ->{
            if(e.length() >= 3){
                return;
            }
            System.out.println(e);
        });