Java8新特性（Stream流）

 public static void main(String[] args) {
        List names = new ArrayList<>();
        Collections.addAll(names,"张无忌","张三丰","周芷若","张强","赵敏");
        System.out.println(names);
        //找到所有姓张的，且只有三个字
       List threeName = new ArrayList<>();
       names.forEach(s -> {
           if(s.startsWith("张") && s.length() == 3){
               threeName.add(s);
           }
       });
        System.out.println(threeName);
 
        HashSet hashSet = new HashSet<>();
        //List集合的stream流
        Stream stream = names.stream();
        //Sset集合的stream流
        Stream stream1 = hashSet.stream();
        HashMap hashMap = new HashMap<>();
        //Map集合的stream流，需要用存放键值对的entrySet
        Set> entries = hashMap.entrySet();
        Stream> stream2 = entries.stream();
        String[] strings = {"1","2","3","4"};
        //数组获取流的方法
        Stream stream3 = Arrays.stream(strings);
        stream3.filter(new Predicate() {
            @Override
            public boolean test(String s) {
                //s是stream流里面的元素
                System.out.println(s);
                return s.startsWith("张") && s.length() == 3;
            }
        });
        //stream是获取的流对象，filter中间添加了过滤条件，collect终结方法，流式编程（链式编程）
        Set set = stream.filter(s -> s.startsWith("张") && s.length() == 3).collect(Collectors.toSet());
        System.out.println(set);
    }