Extension Methods in Java, Xtend and Scala

1_Sample.java

/* JAVA */

public class SampleExtensions {

    public static String sort(String s) {
        final char[] arr = s.toCharArray();
        java.util.Arrays.sort(arr);
        return String.valueOf(arr);
    }

    public static int checksum(String s) {
        int i = 0;
        for (char c : s.toCharArray()) { i += c; }
        return i;
    }

    public static String toUpper(String s) {
        return s.toUpperCase();
    }

}

// bug? static imports from default package do not work for me!?
import static SampleExtensions.*;

public class Sample {

    public static void main(String[] args) {

        // explicitly use extensions
        final String sorted = SampleExtensions.sort("Sort me!");
        System.out.println(sorted);

        final int summed = SampleExtensions.checksum("Sum me!");
        System.out.println(summed);

        final String string = SampleExtensions.toUpper("Upper me!");
        System.out.println(string);

    }

}

2_Sample.xtend

/* XTEND */

// extensions globally usable
import static extension SampleExtensions.*

class SampleExtensions {

    def static sort(String it) {
        toCharArray.sort.join
    }

    def static checksum(String it) {
        toCharArray.fold(0)[a,b | a + b]
    }

    def static toUpper(String it) {
        toUpperCase
    }

}

class Sample {

    def static void main(String[] args) {

        val sorted = "Sort me!".sort
        println(sorted)

        val summed = "Sum me!".checksum
        println(summed)

        val string = "Upper me!".toUpper
        println(string)

    } 

}

3_Sample.scala

/* SCALA */

object SampleImplicits {

    // mention class to be extended only once
    implicit def stringWrapper(s: String) = new {

        def sort() = s.sortWith(_ < _)

        def checksum() = s.map(_.toInt).reduce(_ + _)

        def toUpper() = s.toUpperCase

    }

}

object Sample {

    def main(args: Array[String]) = {

        // use extensions where they are needed
        import SampleImplicits._

        val sorted = "Sort me!".sort
        println(sorted)

        val summed = "Sum me!".checksum
        println(summed)

        val string = "Upper me!".toUpper
        println(string)

    }

}