Java 8 – 从Stream过滤空值

让我们看看一个包含null值的Stream

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

解决方法

可以使用Stream.filter(x -> x!=null)的方法解决。

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 -&gt; x!=null).collect(Collectors.toList());

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


    }
}

output

java
python
node
ruby
php

也可以用Objects::nonNull方法来替代。

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][]

[Java 8 Collectors JavaDoc]: https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html