Add chain methods support groupBy(), indexBy() and countBy().

Author: javadev

src/main/java/com/github/underscore/$.java

@@ -1685,14 +1685,22 @@ public <F extends Comparable<? super F>> Chain<T> sortBy(final Function1<T, F> f
             return new Chain<T>($.sortBy(list, func));
         }
 
-        public <K, V> Chain<Map<K, V>> toMap() {
-            return new Chain<Map<K, V>>($.toMap((Iterable<Map.Entry<K, V>>) list));
-        }
-
         public <K, V extends Comparable<? super V>> Chain<Map<K, V>> sortBy(final K key) {
             return new Chain<Map<K, V>>($.sortBy((List<Map<K, V>>) list, key));
         }
 
+        public <F> Chain<Map<F, List<T>>> groupBy(final Function1<T, F> func) {
+            return new Chain<Map<F, List<T>>>($.groupBy(list, func));
+        }
+
+        public Chain<Map<Object, List<T>>> indexBy(final String property) {
+            return new Chain<Map<Object, List<T>>>($.indexBy(list, property));
+        }
+
+        public <F> Chain<Map<F, Integer>> countBy(final Function1<T, F> func) {
+            return new Chain<Map<F, Integer>>($.countBy(list, func));
+        }
+
         public Chain<T> shuffle() {
             return new Chain<T>($.shuffle(list));
         }
@@ -1750,6 +1758,10 @@ public <T> Chain<T> limit(final int size) {
             return new Chain<T>((List<T>) list.subList(0, size));
         }
 
+        public <K, V> Chain<Map<K, V>> toMap() {
+            return new Chain<Map<K, V>>($.toMap((Iterable<Map.Entry<K, V>>) list));
+        }
+
         public T item() {
             return item;
         }

src/test/java/com/github/underscore/CollectionsTest.java

@@ -785,6 +785,14 @@ public Integer apply(Integer item) {
             }
         });
         assertEquals("[5, 4, 6, 3, 1, 2]", resultObj.toString());
+        final List<Integer> resultChain =
+        $.chain(asList(1, 2, 3, 4, 5, 6)).sortBy(
+            new Function1<Integer, Integer>() {
+            public Integer apply(Integer item) {
+                return Double.valueOf(Math.sin(item) * 1000).intValue();
+            }
+        }).value();
+        assertEquals("[5, 4, 6, 3, 1, 2]", resultChain.toString());
     }
 
 /*
@@ -836,6 +844,14 @@ public Double apply(Double num) {
             }
         });
         assertEquals("{1.0=[1.3], 2.0=[2.1, 2.4]}", resultObj.toString());
+        final Map<Double, List<Double>> resultChain =
+        (Map<Double, List<Double>>) $.chain(asList(1.3, 2.1, 2.4)).groupBy(
+            new Function1<Double, Double>() {
+            public Double apply(Double num) {
+                return Math.floor(num);
+            }
+        }).item();
+        assertEquals("{1.0=[1.3], 2.0=[2.1, 2.4]}", resultChain.toString());
     }
 
 /*
@@ -866,6 +882,10 @@ public String toString() {
         final Map<String, List<Person>> resultObj =
         new $(asList(new Person("moe", 40), new Person("larry", 50), new Person("curly", 60))).indexBy("age");
         assertEquals("{40=[moe, 40], 50=[larry, 50], 60=[curly, 60]}", resultObj.toString());
+        final Map<String, List<Person>> resultChain =
+        (Map<String, List<Person>>) $.chain(asList(new Person("moe", 40), new Person("larry", 50),
+            new Person("curly", 60))).indexBy("age").item();
+        assertEquals("{40=[moe, 40], 50=[larry, 50], 60=[curly, 60]}", resultChain.toString());
         final Map<String, List<Person>> result2 =
         $.indexBy(asList(new Person("moe", 40), new Person("larry", 50), new Person("curly", 60)), "age2");
         assertEquals("{null=[moe, 40, larry, 50, curly, 60]}", result2.toString());
@@ -905,6 +925,15 @@ public String apply(Person person) {
             }
         });
         assertEquals("{moe=2, curly=1}", resultObj.toString());
+        final Map<String, Integer> resultChain =
+        (Map<String, Integer>) $.chain(asList(new Person("moe", 40), new Person("moe", 50),
+            new Person("curly", 60))).countBy(
+            new Function1<Person, String>() {
+            public String apply(Person person) {
+                return person.name;
+            }
+        }).item();
+        assertEquals("{moe=2, curly=1}", resultChain.toString());
     }
 
 /*