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

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

javapythonnodenull   // <--- NULLrubynull   // <--- NULLphp

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

javapythonnoderubyphp

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