publicclassOptionalDemo{//methods from 2.1 to 2.5publicstaticvoidmain(String[] args){ optionalWithStream();// 输出:Get WANG ER with family name Wang!Personperson=newPerson();//fetchPersonFromSomewhereElse()System.out.println(newOptionalDemo().fromWhere(person));// 输出:from NowhereList<Person>...
//ThreadTest.java 源码classMyThreadextendsThread{privateintticket=10;publicvoidrun(){for(inti=0;i<20;i++){if(this.ticket>0){ System.out.println(this.getName()+" 卖票:ticket"+this.ticket--); } } } };publicclassThreadTest {publicstaticvoidmain(String[] args) {//启动3个线程t1,t2,t3...
因为Optional中只有一个值,所以这里的filter实际上是判断单个值是不是。 对比代码: public static Insurance getPinanInsurance(Person person){ Optional<Insurance> insuranceOptional = Optional.ofNullable(person).map(Person::getCar).map(Car::getInsurance); if (insuranceOptional.isPresent() && Objects.equals(...
public<U> Optional<U> flatMap(Function<? super T, Optional<U>> mapper) {} 1. 2. 3. 4. **filter()**方法接受谓词为Predicate类型的函数作为参数,如果value值不为空则自动执行predicate的test()方法(传入时实现),来判断是否满足条件,满足则会返回自身Optional,不满足会返回空Optional;如果value值为空,...
public class OptionalMain{public static void main(String[]args){//创建用户对象 User user=new User();//调用一系列get方法获取身份证号码//因为调用 getIdCard()时并没有身份证对象为null,再调用getIdNum方法则出现 NullPointerException String idNum=user.getIdCard().getIdNum();System.out.println(id...
TheOptionalclass in Java provides a convenient way to handle scenarios where a value may be present or absent, avoiding the need for null checks. TheisPresentandisEmptymethods are used to check the presence or absence of a value within anOptionalobject. By using these methods, we can write ...
class Null2OptionalDemo { public static void main(String[] args) { Optional<List<String...
publicclassNullPointerTest{/*** 需求：根据用户名查找该用户所在的部门名称** @param args*/public...
二、Optional类 一句话介绍Optional类:使用JDK8的Optional类来防止NPE(空指针异常)问题。 接下来我们看看文档是怎么说的: A container object which may or may not contain a non-null value.Additional methods that depend on the presence or absence of a contained value are provided ...
Methods 展开表 Clone() Creates and returns a copy of this object. (Inherited fromObject) Dispose()(Inherited fromObject) Dispose(Boolean)(Inherited fromObject) Empty() Returns an emptyOptionalinstance. Equals(Object) Indicates whether some other object is "equal to" this one. ...