Added exercise accumulate

accumulate/build.gradle

@@ -0,0 +1,11 @@
+apply plugin: "java"
+apply plugin: "eclipse"
+apply plugin: "idea"
+
+repositories {
+  mavenCentral()
+}
+
+dependencies {
+  testCompile "junit:junit:4.10"
+}

accumulate/example.java

@@ -0,0 +1,17 @@
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.function.Function;
+
+public class Accumulate {
+
+	public static <T> Collection<T> accumulate(Collection<T> collection, Function<T, T> function) {
+		List<T> newCollection = new ArrayList<>();
+
+		for (T item : collection) {
+			newCollection.add(function.apply(item));
+		}
+
+		return newCollection;
+	}
+}

accumulate/src/main/java/Accumulate.java

@@ -0,0 +1,2 @@
+public class Accumulate {
+}

accumulate/src/test/java/AccumulateTest.java

@@ -0,0 +1,53 @@
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class AccumulateTest {
+
+    @Test
+    public void emptyAccumulateProducesEmptyAccumulation() {
+        List<Integer> input = new LinkedList<>();
+        List<Integer> expectedOutput = new LinkedList<>();
+        assertEquals(expectedOutput, Accumulate.accumulate(input, x -> x * x));
+    }
+
+    @Test
+    public void accumulateSquares() {
+        List<Integer> input = Arrays.asList(1, 2, 3);
+        List<Integer> expectedOutput = Arrays.asList(1, 4, 9);
+        assertEquals(expectedOutput, Accumulate.accumulate(input, x -> x * x));
+    }
+
+    @Test
+    public void accumulateUpperCases() {
+        List<String> input = Arrays.asList("hello", "world");
+        List<String> expectedOutput = Arrays.asList("HELLO", "WORLD");
+        assertEquals(expectedOutput, Accumulate.accumulate(input, x -> x.toUpperCase()));
+    }
+
+    @Test
+    public void accumulateReversedStrings() {
+        List<String> input = Arrays.asList("the quick brown fox etc".split(" "));
+        List<String> expectedOutput = Arrays.asList("eht kciuq nworb xof cte".split(" "));
+        assertEquals(expectedOutput, Accumulate.accumulate(input, this::reverse));
+    }
+
+    private String reverse(String input) {
+        return new StringBuilder(input).reverse().toString();
+    }
+
+    @Test
+    public void accumulateWithinAccumulate() {
+        List<String> input1 = Arrays.asList("a", "b", "c");
+        List<String> input2 = Arrays.asList("1", "2", "3");
+        List<String> expectedOutput = Arrays.asList("a1 a2 a3", "b1 b2 b3", "c1 c2 c3");
+        assertEquals(expectedOutput, Accumulate.accumulate(
+                input1, c ->
+                        String.join(" ", Accumulate.accumulate(input2, d -> c + d))
+        ));
+    }
+}

config.json

@@ -24,7 +24,8 @@
     "raindrops",
     "allergies",
     "strain",
-    "atbash-cipher"
+    "atbash-cipher",
+    "accumulate"
   ],
   "deprecated": [
   ],