Java Functions as Objects

Question

I have a very good use for having functions as objects in Java, aka the following sort of thing:

Function handle_packet_01 = void handle() {}

I don't want to use Scala because I can't stand the syntax.

Is there any sort of hack that I can apply to the JVM to allow me to do this? How about an Eclipse plugin?

I saw a similar sort of thing for operator overloading in Java, which I am going to install the plugin for too.

Please read about java 8 api oracle.com/webfolder/technetwork/tutorials/obe/java/… Additionally, You can simulate such approach with creating interface with syntax of handle method. — gauee
– gauee, Commented Dec 8, 2015 at 20:31
Thanks, I will go and read up about it now. Since this is just for a server, Java 8 is good. — Lucien
– Lucien, Commented Dec 8, 2015 at 20:34
@GergelyBacso, there's an Eclipse plugin that lets you use operator overloading in your Java code, so anything's possible, right? — Lucien
– Lucien, Commented Dec 8, 2015 at 20:42
Thanks to those who suggested lambdas, they're perfect for this. — Lucien
– Lucien, Commented Dec 8, 2015 at 20:42

gibertoni · Accepted Answer · 2015-12-09 16:59:31Z

1

In Java 8 you can reference a member method as following

MyClass::function

EDIT: A more complete example

//For this example I am creating an interface that will serve as predicate on my method
public interface IFilter
{
   int[] apply(int[] data);
}

//Methods that follow the same rule for return type and parameter type from IFilter may be referenced as IFilter
public class FilterCollection
{
    public static int[] median(int[]) {...}
    public int[] mean(int[]) {...}
    public void test() {...}
}

//The class that we are working on and has the method that uses an IFilter-like method as reference
public class Sample
{
   public static void main(String[] args)
   {
       FilterCollection f = new FilterCollection();
       int[] data = new int[]{1, 2, 3, 4, 5, 6, 7};

      //Static method reference or object method reference
      data = filterByMethod(data, FilterCollection::median);
      data = filterByMethod(data, f::mean);

      //This one won't work as IFilter type
      //data = filterByMethod(data, f::test); 
   }

   public static int[] filterByMethod(int[] data, IFilter filter)
   {
       return filter.apply(data);
   }

}

Also take a look at lambda expressions for another example and usage of method reference

edited Dec 9, 2015 at 16:59

answered Dec 8, 2015 at 20:39

gibertoni

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2 Comments

Lucien Over a year ago

Quick question, what is the type of FIlter::median?

gibertoni Over a year ago

@Lolums I have now provided a better and more complete example.

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