复习一个Stream 包含 null 数据的例子.

Java8Examples.java

package com.mkyong.java8; import java.util.List; import java.util.stream.Collectors; import java.util.stream.Stream; public class Java8Examples { public static void main(String[] args) { Stream<String> language = Stream.of("java", "python", "node", null, "ruby", null, "php"); List<String> result = language.collect(Collectors.toList()); result.forEach(System.out::println); } }

output

java
python
node
null   // <--- NULL
ruby
null   // <--- NULL
php

Solution（解决）

为了解决上面的问题，我们使用： Stream.filter(x -> x!=null)

Java8Examples.java

package com.mkyong.java8; import java.util.List; import java.util.stream.Collectors; import java.util.stream.Stream; public class Java8Examples { public static void main(String[] args) { Stream<String> language = Stream.of("java", "python", "node", null, "ruby", null, "php"); //List<String> result = language.collect(Collectors.toList()); List<String> result = language.filter(x -> x!=null).collect(Collectors.toList()); result.forEach(System.out::println); } }

output

java
python
node
ruby
php

另外，过滤器还可以用： Objects::nonNull

import java.util.List; List<String> result = language.filter(Objects::nonNull).collect(Collectors.toList());

References

1. Objects::nonNull JavaDoc
2. Java 8 Streams filter examples
3. Java 8 Collectors JavaDoc