第二部分:Java 8 Optional 的引入 Optional 的概念 Optional是一个容器,表示一个可能存在或不存在的值。它的设计目的是提供一种更清晰的方式来处理缺失值。 importjava.util.Optional;publicclassOptionalExample{publicstaticvoidmain(String[] args){ Optional<String> optionalValue = Optional.of("Hello"); System...
Exception in thread"main"java.lang.NullPointerException at java.util.Objects.requireNonNull(Objects.java:203) at java.util.Optional.<init>(Optional.java:96) at java.util.Optional.of(Optional.java:108) at club.mydlq.OptionalExample.main(OptionalExample.java:12) 可以看到传入正常参数正常返回 Optiona...
在Java 8之前,Google Guava引入了Optionals类来解决NullPointerException,从而避免源码被各种null检查污染,以便开发者写出更加整洁的代码。 Java 8也将Optional加入了官方库。 Optional仅仅是一个功能:存放T类型的值或者null。它提供了一些有用的接口来避免显式的null检查,可以参考Java 8官方文档...
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...
Often we need to call a method on an object and check some property. For example, in below code, we check if the company has a ‘Finance’ department; if it has, then print it. Optional<Company>companyOptional=Optional.empty();companyOptional.filter(department->"Finance".equals(department....
传入正常参数:mydlq Exception in thread "main" java.util.NoSuchElementException: No value present at java.util.Optional.get(Optional.java:135) at club.mydlq.OptionalExample.main(OptionalExample.java:14) 可以观察到传入正常值的 Optional 调用 get 方法正常输出值,通过空的 optional 对象使用 get 方法...
java8新特性,optional类,还在 if(obj==null)?太low了! 作为一名java开发人员,每个人都会遇到这样的问题:调用一个方法得到了返回值却不能直接将返回值作为参数去调用别的方法。我们首先要判断这个返回值是否为null,只有在非空的前提下才能将其作为其他方法的参数。否则就会出现NPE异常,就是传说中的空指针异常。
Java 8 – Optional.map and Optional.flatMap In this example, we will see how Optional works with map and flatMap. //Importing Optional class import java.util.Optional; public class Example { public static void main(String[] args) { //Creating Optional object from a String Optional<String>...
Let’s now look at how the above code could be refactored in Java 8. In typical functional programming style, we can execute perform an action on an object that is actually present: In the above example, we use only two lines of code to replace the five that worked in the first examp...
This method supports post-processing on optional values, without the need to explicitly check for a return status. For example, the following code traverses a stream of file names, selects one that has not yet been processed, and then opens that file, returning anOptional<FileInputStream>: ...