首先,重构类,使其 getter 方法返回Optional引用: publicclassUser{privateAddress address;publicOptional<Address>getAddress(){returnOptional.ofNullable(address); }// ...}publicclassAddress{privateCountry country;publicOptional<Country>getCountry(){returnOptional.ofNullable(country); }// ...} 上面的嵌套结构...
实例 importjava.util.Optional;importjava.util.function.Supplier;publicclassTester{publicstaticvoidmain(String[]args){Optional<String>optional1=Optional.of("Mahesh");Supplier<Optional<String>>supplierString=()->Optional.of("Not Present");optional1=optional1.or(supplierString);optional1.ifPresent(x->S...
该类主要用来处理几乎每位程序员都碰到过的麻烦问题—— 空指针异常(NullPointerException)。 从本质上来说,该类属于包含可选值的封装类(wrapper class),因此它既可以包含对象也可以仅仅为空。 伴随着Java函数式编程方式的异军突起,Optional 应运而生,除了可助该编程方式一臂之力外,Optional 的作用显然还远不止于...
[Android.Runtime.Register("java/util/Optional", ApiSince=24, DoNotGenerateAcw=true)] [Java.Interop.JavaTypeParameters(new System.String[] { "T" })] public sealed class Optional : Java.Lang.Object Inheritance Object Object Optional Attributes ...
为了解决这种尴尬的处境,JDK 终于在 Java8 的时候加入了 Optional 类。用于避免空指针的出现,也无需在写大量的if(obj!=null)这样的判断了,前提是你得将数据用Optional装着,它就是一个包裹着对象的容器。 Optional 的 javadoc 介绍: A container object which may or may not contain a non-nullvalue. If a...
Class Optional<T> 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. ...
Java documentation forjava.util.OptionalInt. Portions of this page are modifications based on work created and shared by theAndroid Open Source Projectand used according to terms described in theCreative Commons 2.5 Attribution License. Properties ...
Java.Util Assembly: Mono.Android.dll A container object which may or may not contain a non-nullvalue. C#Copiar [Android.Runtime.Register("java/util/Optional", ApiSince=24, DoNotGenerateAcw=true)] [Java.Interop.JavaTypeParameters(new System.String[] {"T"})]publicsealedclassOptional:Java.Lan...
Added in 1.8. Java documentation forjava.util.OptionalDouble. Portions of this page are modifications based on work created and shared by theAndroid Open Source Projectand used according to terms described in theCreative Commons 2.5 Attribution License. ...
Overrides: hashCodein classObject Returns: hash code value of the present value or 0 if no value is present See Also: Object.equals(java.lang.Object),System.identityHashCode(java.lang.Object)