List<User> userList = handleUser();
        List<User> geUser = new ArrayList<>();
        for (User user : userList) {
            if (user.getAge() > 20){
                geUser.add(user);
            }
        }

handleUser(){
        List<User> userList = new ArrayList<>();
        User user = new User();
        user.setId(UUID.randomUUID().toString());
        user.setName("張三");
        user.setAge(20);
        user.setDept("開發(fā)部");
        userList.add(user);

        User user1 = new User();
        user1.setId(UUID.randomUUID().toString());
        user1.setName("李四");
        user1.setAge(22);
        user1.setDept("測(cè)試部");
        userList.add(user1);

        User user2 = new User();
        user2.setId(UUID.randomUUID().toString());
        user2.setName("王五");
        user2.setAge(27);
        user2.setDept("財(cái)務(wù)部");
        userList.add(user2);

        return userList;

    }

List<User> geUserStream = userList.stream().filter(e -> e.getAge() > 20).collect(Collectors.toList());

JDK7中的for循環(huán)
for (User user : collect) {
            System.out.println("年齡大于20的人是:"+user.getName());
        }

JDK8的for循環(huán)
        collect.stream().forEach(vo->{
            System.out.println("年齡大于20的人是:"+vo.getName());
        });

//JDK7 獲取List<String> 中字符串最長的那個(gè)
        String[] strArr = new String[] { "cd", "ab", "ddfa", "sd", "zd" };
        List<String> list = Arrays.asList(strArr);
        String max = Collections.max(list, new Comparator<String>() {
            @Override
            public int compare(String o1, String o2) {
                if (o1.length() < o2.length()) {
                    return -1;
                }
                if (o1.length() == o2.length()) {
                    return o1.compareTo(o2);
                } else {
                    return 1;
                }
            }
        });
        System.out.println(max);

JDK8獲取List<String>中最長的字符串

        String[] strArr = new String[] { "cd", "ab", "ddfa", "sd", "zd" };
        List<String> list = Arrays.asList(strArr);
        Optional<String> max = list.stream().max(Comparator.comparing(String::length));
        System.out.println(max.get());

List<Integer> numList = Arrays.asList(42, 44, 43, 41); 

//獲取List中大于43的元素的個(gè)數(shù)

        long count = numList.stream().filter(e -> e > 43).count();
        System.out.println(count);

//給List賦值
List<User> list = getList();
//新的IdList
List<String> Ids = new ArrayList<>();
  for (User user: list) {
      Ids.add(user.getId());
  }