java8 回调新写法和空指针处理

@FunctionalInterfacepublic interface iplay {    String   show(String msg);    default  String  make(){        return "make";    }}
public class Person {     PRivate  String  userName;     private  String  passWord;    public String getUserName() {        return userName;    }    public void setUserName(String userName) {        this.userName = userName;    }    public String getPassword() {        return password;    }    public void setPassword(String password) {        this.password = password;    }}
import java.util.Optional;public class Main {    public static void main(String[] args) {        IPlay  play1 = new IPlay() {            @Override            public String show(String msg) {                return "原来的写法如下";            }        };        // 现在的写法        IPlay  play = (msg)->{return  msg;};        String msg  = play.show("我是消息");        System.out.println(msg);        msg =  play.make();        System.out.println(msg);        // Optional 更多的体现是一个容器，包含null的一个容器。通过他去判断。        Person person = null;        Optional<Person>  optional = Optional.ofNullable(person);        boolean flag = optional.isPresent();        System.out.println(flag);        if (flag){             person = optional.get(); // 获取对象进行处理。             System.out.println(person);        }else{            System.out.println("person is null");        }    }}