Review a Stream containing null values.
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
To solve it, uses 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
Alternatively, filter with Objects::nonNull
import java.util.List;
List<String> result = language.filter(Objects::nonNull).collect(Collectors.toList());
How to check null for list of Bean property
Objects::nonNull is recommended by Sonar
Is there a solution to this?
public void consume(@Nonnull string) {
// ...
}
public run() {
Steam<@Nullable String> stream = Stream.of("hello", null, "world");
stream.filter(Objects::nonNull).forEach(this::consume); // XXX this causes null-warnings because the filter-call does not change the nullness of the stream parameter
}
I have a solution using flatMap(), but it would be much nicer if the filter method could just return @Nonnull String when called using the Objects::nonNull function.
What if all elements are null? It will fail in the Collect or if I may have a mapping before collecting?
What about .filter(Objects::nonNull)
It really helped me.. thank you so much