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Tip: Allow Only One Null Property

See how to use Stream API to figure out which properties should be set to null or non-null.


Consider a Review object with three properties: article, book and magazine. Let's assume that only one of these three properties should be set as non-null.

For checking this constraint we can rely on Stream API as below:

return Stream.of(review.getBook(), review.getArticle(), review.getMagazine())
    .count() == 1;


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Octavia Andreea Anghel is a senior PHP developer currently working as a primary trainer for programming teams that participate at national and international software-development contests. She consults on developing educational projects at a national level. She is a coauthor of the book "XML Technologies--XML in Java" (Albastra, ISBN 978-973-650-210-1), for which she wrote the XML portions. In addition to PHP and XML, she's interested in software architecture, web services, UML, and high-performance unit tests.
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