stream流例题

···

public List<User> getUsers(){
    User a = new User(1, "a", 21);
    User b = new User(2, "b", 22);
    User c = new User(3, "c", 23);
    User d = new User(4, "d", 24);
    User f = new User(5, "f", 25);
    List<User> asList =  Arrays.asList(a, b, c, d, f);
    return  asList;
}
/**
 * 1,ID必须是偶数的
 */
public void test1(){
    List<User> users = this.getUsers();
    List<User> collect = users.stream().filter(item -> item.getId() % 2 == 0).collect(Collectors.toList());
    System.out.println(JSON.toJSON(collect));
}

/**
 * 2，年龄必须大于25岁
 */
public void test2(){
    List<User> users = this.getUsers();
    List<User> collect = users.stream().filter(item -> item.getAge() > 23 ).collect(Collectors.toList());
    System.out.println(JSON.toJSON(collect));
}


/**
 * 3，用户名转大写
 */
public void test3(){
    List<User> users = this.getUsers();
     users.forEach(item->item.setName(  item.getName().toUpperCase()));
    System.out.println(JSON.toJSONString(users));
}
/**
 * 4，用户名字母倒叙
 */
public void tes4(){
    List<User> users = this.getUsers();
    users.stream().sorted(Comparator.comparing(User::getName));
}


/**
 * 5，只输出一个用户
 */
public void test5(){
    List<User> users = this.getUsers();
    Stream<User> limit = users.stream().limit(1);
}

···