Java 8 – 从一个 Stream中过滤null值

复习一个Stream 包含 null 数据的例子.

Java8Examples.java

1. package com.mkyong.java8;

2.  

3. import java.util.List;

4. import java.util.stream.Collectors;

5. import java.util.stream.Stream;

6.  

7. public class Java8Examples {

8.  

9. public static void main(String[] args) {

10.  

11. Stream<String> language = Stream.of("java", "python", "node", null, "ruby", null, "php");

12.  

13. List<String> result = language.collect(Collectors.toList());

14.  

15. result.forEach(System.out::println);

16.  

17. }

18. }

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

1. package com.mkyong.java8;

2.  

3. import java.util.List;

4. import java.util.stream.Collectors;

5. import java.util.stream.Stream;

6.  

7. public class Java8Examples {

8.  

9. public static void main(String[] args) {

10.  

11. Stream<String> language = Stream.of("java", "python", "node", null, "ruby", null, "php");

12.  

13. //List<String> result = language.collect(Collectors.toList());

14.  

15. List<String> result = language.filter(x -> x!=null).collect(Collectors.toList());

16.  

17. result.forEach(System.out::println);

18.  
19.  

20. }

21. }

output

java
python
node
ruby
php

另外，过滤器还可以用： Objects::nonNull

1. import java.util.List;

2.  

3. 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