IntStream strange error

Question

Java 8 has a new interface, named IntStream. I used its of() static method and encountered a strange error:

This static method of interface IntStream can only be accessed as IntStream.of

But as you can see in the following code, I, exactly, used IntStream.of

import java.util.stream.IntStream;

public class Test {

    public static void main(String[] args) {
        int[] listOfNumbers = {5,4,13,7,7,8,9,10,5,92,11,3,4,2,1};
        System.out.println(IntStream.of(listOfNumbers).sum());
    }

}

Moreover, if you check the API, you will see that the method has been declared in the similar way which I used.

Answer 1

You need to set the project to use Java 8. For example if you are using maven, place the following snippet in your pom:

 <build>
      <pluginManagement>
           <plugins>
                <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-compiler-plugin</artifactId>
                     <version>3.2</version>
                     <configuration>
                          <source>1.8</source>
                          <target>1.8</target>
                     </configuration>
                </plugin>
           </plugins>
      </pluginManagement>
 </build>

Answer 2

Although IntStream.of(int...) seems to work it is more likely that you are expected to use Arrays.stream(int[]).

public void test() {
    int[] listOfNumbers = {5, 4, 13, 7, 7, 8, 9, 10, 5, 92, 11, 3, 4, 2, 1};
    // Works fine but is really designed for ints instead of int[]s.
    System.out.println(IntStream.of(listOfNumbers).sum());
    // Expected use.
    System.out.println(IntStream.of(5, 4, 13, 7, 7, 8, 9, 10, 5, 92, 11, 3, 4, 2, 1).sum());
    // Probably a better approach for an int[].
    System.out.println(Arrays.stream(listOfNumbers).sum());
}