June 2018 Update

Task/List-comprehensions/Java/list-comprehensions.java

@@ -0,0 +1,33 @@
+// Boilerplate
+import java.util.Arrays;
+import java.util.List;
+import static java.util.function.Function.identity;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.IntStream.range;
+public interface PythagComp{
+    static void main(String... args){
+        System.out.println(run(20));
+    }
+
+    static List<List<Integer>> run(int n){
+        return
+            // Here comes the list comprehension bit
+            // input stream - bit clunky
+            range(1, n).mapToObj(
+                x -> range(x, n).mapToObj(
+                    y -> range(y, n).mapToObj(
+                        z -> new Integer[]{x, y, z}
+                    )
+                )
+            )
+                .flatMap(identity())
+                .flatMap(identity())
+                // predicate
+                .filter(a -> a[0]*a[0] + a[1]*a[1] == a[2]*a[2])
+                // output expression
+                .map(Arrays::asList)
+                // the result is a list
+                .collect(toList())
+        ;
+    }
+}