java stream 泛型

调用stream时,必须明确集合的泛型

        List list1 = Arrays.asList("1","2","3");
        list1.stream().filter(x->x.length()>=1).forEach(System.out::println);//报错,x被当成object来处理

要改成

        List<String> list1 = Arrays.asList("1","2","3");//指明集合类型是String
        list1.stream().filter(x->x.length()>=1).forEach(System.out::println);