写几个有用的lambda

　　　　　List<String> list = Arrays.asList("app", "ban", "ora");

        //循环输出
        for (String s : list) {
            System.out.println(s);
        }
        list.forEach(System.out::println);

        //排序
        Collections.sort(list, new Comparator<String>() {
            @Override
            public int compare(String o1, String o2) {
                return o1.compareTo(o2);
            }
        });
        Collections.sort(list,(o1, o2) -> o1.compareTo(o2));

        //过滤
        List<String>list1=new ArrayList<>();
        for (String s:list) {
            if(s.startsWith("a"))
                list1.add(s);
        }
        List<String>list2=list.stream().filter(s -> s.startsWith("a")).collect(Collectors.toList());

        //映射
        List<Integer>list3=new ArrayList<>();
        for (String s:list) {
            list3.add(s.length());
        }
        List<Integer>list4=list.stream().map(String::length).collect(Collectors.toList());

        //分组
        Map<Integer,List<String>>groups=new HashMap<>();
        for (String s:list) {
            int l=s.length();
            if(!groups.containsKey(l)){
                groups.put(l,new ArrayList<>());
            }
            groups.get(l).add(s);
        }
        Map<Integer,List<String>>groups1=list.stream().collect(Collectors.groupingBy(String::length));

        //混用案例
        List<String>list5=new ArrayList<>();
        for (String s:list) {
            if(s.startsWith("a")){
                list5.add(s.toUpperCase());
            }
        }
        Collections.sort(list5);
        List<String>list6=list.stream().
                filter(s -> s.startsWith("a")).
                map(s -> s.toUpperCase()).
                sorted().collect(Collectors.toList());