isPresent() will return true and get() will return the value.Additional methods that depend on t...
具体可以参考这个答案Optional无疑是一个糟糕的设计，更适合 Java 的演化方向应该是在 Java 8 时增强空...
publicstaticStringinWhichCityLowercaseTU(Person person){//Traditional&Uglyif(person !=null) {Locationlocation=person.getLocation();if(location !=null) {Stringcity=location.getCity();if(city !=null) {returncity.toLowerCase(); }else{return"nowhere"; } }else{return"nowhere"; } }else{return"no...
Rule 4: It's generally a bad idea to create an Optional for the specific purpose of chaining methods from it to get a value. 链式语法可以让代码的处理流程看起来更加清晰,但是为了链式而去使用Optional的话,在某些情况下并不会显得有多优雅 比如,本来可以使用三目运算 String process(String s) { ret...
import java.util.function.Supplier; /** * A container object which may or may not contain a non-null value. * If a value is present, {@code isPresent()} will return {@code true} and * {@code get()} will return the value. * * Additional methods that depend on the presence or a...
* method is designed primarily for doing parameter validation in methods * and constructors, as demonstrated below: * <blockquote> * public Foo(Bar bar) { * this.bar = Objects.requireNonNull(bar); * } * </blockquote> * * @param ...
* Additional methods that depend on the presence or absence of a contained * value are provided, such as {@link #orElse(java.lang.Object) orElse()} * (return a default value if value not present) and * {@link #ifPresent(java.util.function.Consumer) ifPresent()} (execute a block ...
原题: Understanding, Accepting and Leveraging Optional inJava 编者按:Java 9终于在9月21号发布,于是知乎上关于“现在Java初学用等Java9出来再学吗”之类的问题可能有更新。在 Java 8 引入Optional特性的基础上,Java 9 又为 Optional 类增加了三种方法:or()、ifPresentOrElse() 和 stream(),本文的最后,也针对...
java.lang.Object java.util.Optional<T> public final classOptional<T>extendsObject A container object which may or may not contain a non-null value. If a value is present,isPresent()will returntrueandget()will return the value. Additional methods that depend on the presence or absence of a...
This essentially means thatOptionalshould be used as the return type of certain service, repository or utility methods only where they truly serve the purpose. 9. Conclusion In this article, we learned how we can adopt the new Java SE 8java.util.Optional. The purpose ofOptionalis not to rep...