MapFunc::map

src/main/java/ArrayListCombiner/ArrayListCombiner.java

@@ -10,9 +10,10 @@ import java.util.ArrayList;
  */
 public class ArrayListCombiner {
     public static <E> void superCombiner(ArrayList<? super E> parent, ArrayList<E> child) {
-        
+        parent.addAll(child);
     }
 
     public static <E> void extendCombiner(ArrayList<E> parent, ArrayList<? extends E> child) {
+        parent.addAll(child);
     }
 }

src/main/java/MapFunc/MapFunc.java

@@ -9,4 +9,12 @@ import java.util.function.Function;
  */
 public class MapFunc {
 
+    public static <T, R> ArrayList<R> map(ArrayList<T> a, Function<T, R> f) {
+
+        ArrayList<R> result = new ArrayList<>(a.size());
+        a.forEach(
+                t -> result.add(f.apply(t))
+        );
+        return result;
+    }
 }

src/test/java/MapFunc/MapFuncTest.java

@@ -1,36 +1,35 @@
-//package MapFunc;
-//
-//import MapFunc.MapFunc;
-//import org.junit.Test;
-//
-//import java.util.ArrayList;
-//import org.junit.Assert;
-//
-//public class MapFuncTest {
-//    @Test
-//    public void testSingleTypeMap() throws Exception {
-//        // Given an integer array list
-//        ArrayList<Integer> intList = new ArrayList<>();
-//        intList.add(1);
-//        intList.add(2);
-//        // When it's mapped with a function to double the value
-//        ArrayList<Integer> mappedList = MapFunc.map(intList, num -> num*2);
-//        // Then all the values are doubled
-//        Assert.assertEquals(new Integer(2), mappedList.get(0));
-//        Assert.assertEquals(new Integer(4), mappedList.get(1));
-//    }
-//
-//    @Test
-//    public void testMultipleTypeMap() throws Exception {
-//        // Given an integer array list
-//        ArrayList<Integer> intList = new ArrayList<>();
-//        intList.add(1);
-//        intList.add(2);
-//        // When it's mapped with to string
-//        ArrayList<String> mappedList = MapFunc.map(intList, num -> num.toString());
-//        // Then all the values are doubled
-//        Assert.assertEquals("1", mappedList.get(0));
-//        Assert.assertEquals("2", mappedList.get(1));
-//    }
-//
-//}
+package MapFunc;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.ArrayList;
+
+public class MapFuncTest {
+    @Test
+    public void testSingleTypeMap() throws Exception {
+        // Given an integer array list
+        ArrayList<Integer> intList = new ArrayList<>();
+        intList.add(1);
+        intList.add(2);
+        // When it's mapped with a function to double the value
+        ArrayList<Integer> mappedList = MapFunc.map(intList, num -> num * 2);
+        // Then all the values are doubled
+        Assert.assertEquals(new Integer(2), mappedList.get(0));
+        Assert.assertEquals(new Integer(4), mappedList.get(1));
+    }
+
+    @Test
+    public void testMultipleTypeMap() throws Exception {
+        // Given an integer array list
+        ArrayList<Integer> intList = new ArrayList<>();
+        intList.add(1);
+        intList.add(2);
+        // When it's mapped with to string
+        ArrayList<String> mappedList = MapFunc.map(intList, num -> num.toString());
+        // Then all the values are doubled
+        Assert.assertEquals("1", mappedList.get(0));
+        Assert.assertEquals("2", mappedList.get(1));
+    }
+
+}