Optional<String> optionalStr = Optional.of(value); System.out.println(optionalStr);// 输出Optional[Hello World] StringnullValue=null; Optional<String> optionalNull = Optional.of(nullValue);// 抛出NullPointerException 2.2.2 ofNullable() 使用ofNullable()方法创建一个Optional对象,如果参数为null,则返回...
1/**2* A container object which may or may not contain a non-null value.3* If a value is present, {@codeisPresent()} will return {@codetrue} and4* {@codeget()} will return the value.5*6*@since1.87*/8publicfinalclassOptional<T>{9/**10* Common instance for {@codeempty()}.1...
package com.wkcto.optional; import java.util.Optional; /** * 演示Optional的基本操作 * Author : 动力节点老崔 */ public class Test01 { public static void main(String[] args) { //1)把一个字符串封装为Optional对象 Optional<String> ofString = Optional.of("wkcto"); //参数不能为null //2)...
publicstaticvoidmain(String[]args){//构造器引用:它的语法是Class::new,或者更一般的Class< T >::new实例如下:final Sky sky=Sky.create(Sky::new);sky.setColor("red");final List<Sky>skys=Arrays.asList(sky);//静态方法引用:它的语法是Class::static_method,实例如下:skys.forEach(Sky::collide);/...
Java 8 通过增加大量新类,扩展已有类的功能的方式来改善对并发编程、函数式编程、日期/时间相关操作以及其他更多方面的支持。 4.1 Optional 到目前为止,臭名昭著的空指针异常是导致Java应用程序失败的最常见原因。以前,为了解决空指针异常,Google公司著名的Guava项目引入了Optional类,Guava通过使用检查空值的方式来防止代码...
Java 8 前言:Java 8 已经发布很久了,很多报道表明Java 8 是一次重大的版本升级。在Java Code Geeks上已经有很多介绍Java 8新特性的文章,例如Playing with Java 8 – Lambdas and Concurrency、Java 8 Date Time API Tutorial : LocalDateTime和Abstract Class Versus Interface in the JDK 8 Era。本文还参考了一些...
1 public class Demo { 2 class Person { 3 private String name = "Hello To Optional"; 4 public Optional getName() { 5 return Optional.ofNullable(name); 6 } 7 } 8 public void optionalMethodDemo() { 9 Person person = new Person(); 10 Optional personOptional = Optional.of(person); ...
Optional reference 1. Overview In this tutorial, we’re going to show theOptionalclass that was introduced in Java 8. The purpose of the class is to provide a type-level solution for representing optional values instead ofnullreferences. ...
optional 是 java 8 新的判空特性，老的判空方法 java public class OptionalDemo { static class A { B b; } static class B { Integer c; } private static A getA() { return new A(); } public static void main(String[] args) { A a = getA(); if...
We can alsoassumeOptionalas a single-value container that either contains a value or doesn’t. It is important to note that the intention of theOptionalclass is not to replace every singlenullreference. Instead, its purpose is tohelp design more-comprehensible APIsso that by just reading the ...