How to determine null traversal by JDK8
Editor to share with you how to JDK8 empty traversal, I believe that most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to understand it!
In the work, often deal with a variety of variables, but often in the use of variables, to make an empty judgment, otherwise an error will be reported.
Java 8 provides the method of writing null:
Optional.ofNullable (variable) .orElse (default)
Example 1: find the length of the string s (return 0 if empty).
Conventional writing:
String s = getKey (); if (s = = null) {return 0;} else {return s.length ();}
Java 8 is written:
String s = getKey (); return Optional.ofNullable (s) .orElse (") .length ()
Example 2: loop through the collection
Conventional writing:
List list = getList (); if (list! = null) {for (String s: list) {System.out.println (s);}}
Java 8 is written:
List list = getList (); Optional.ofNullable (list) .orElse (new ArrayList ()) .forEach (o-> {System.out.println (o);})
PS: use Optional to avoid NullPointerException caused by null
Null pointer exceptions are the most common cause of Java application failure. In the past, to solve null pointer exceptions, Google's famous Guava project introduced the Optional class. Guava prevents code contamination by checking null values, which encourages programmers to write cleaner code. Inspired by Google Guava, the Optional class has become part of the Java 8 class library. Optional is actually a container: it can hold the value of type T, or just null. Optional provides a lot of useful methods so that we don't have to explicitly detect null values.
Optional.of () or Optional.ofNullable (): create an Optional object, the difference being that of does not allow the argument to be null, while ofNullable has no restrictions.
/ / Parameter cannot be nullOptional optional1 = Optional.of (1); / / Parameter can be nullOptional optional2 = Optional.ofNullable (null); / / Parameter can be non-nullOptional optional3 = Optional.ofNullable (2)
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