Using Optional

https://blog.kaaass.net/archives/764

public static String getName(User u) {     return Optional.ofNullable(u)                     .map(user->user.name)                     .orElse("Unknown"); }

public static String getChampionName(Competition comp) throws IllegalArgumentException {

    return Optional.ofNullable(comp)

            .map(c->c.getResult())

            .map(r->r.getChampion())

            .map(u->u.getName())

            .orElseThrow(()->new IllegalArgumentException("The value of param comp isn't available."));

}

还有很多不错的使用姿势，比如为空则不打印可以这么写：

Java

1	string.ifPresent(System.out::println);

Optional的魅力还不止于此，Optional还有一些神奇的用法，比如Optional可以用来检验参数的合法性。

Java

1 2 3 4

public void setName(String name) throws IllegalArgumentException {     this.name = Optional.ofNullable(name).filter(User::isNameValid)                         .orElseThrow(()->new IllegalArgumentException("Invalid username.")); }