英文:
How to handle NPE in the intermediate operations of Optional/Stream?
问题
public class Person {private String name;private Address address;}public class Address {private City city;}public class City {private String name;}Optional.ofNullable(Person::getAddress).map(address -> Optional.ofNullable(address.getCity()).map(City::getName).orElse(null)).orElseThrow();
在这里处理空指针异常的最佳方法是使用Optional的ofNullable方法来包装可能为null的值。首先，使用ofNullable包装getAddress方法的调用，然后在第一个.map中对address对象进行处理。在内部的Lambda表达式中，再次使用ofNullable来包装getCity方法的调用，然后使用第二个.map来处理City对象的名字。最后，使用orElse(null)来处理整个链中的空值，然后调用orElseThrow来抛出异常。
英文:
public class Person {private String name;private Address address;}public class Address {private City city}public class City {private String name;}Optional.of(Person::getAddress).map(Address::getCity).map(City::getName).orElseThrow();
The middle two .map may throw NPE because getAddress and getCity may return null. What's the best approach to handle NPE here?
答案1
得分: 2
Person person = new Person();Optional.ofNullable(person.getAddress()).flatMap(p -> Optional.of(p.getCity())).flatMap(c -> Optional.of(c.getName())).orElseThrow(NullPointerException::new);
英文:
Person person = new Person();Optional.ofNullable(person.getAddress()).flatMap(p -> Optional.of(p.getCity())).flatMap(c -> Optional.of(c.getName())).orElseThrow(NullPointerException::new);
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