Add IndexOf method to ArrayList

lists/arraylist/arraylist.go

@@ -98,6 +98,18 @@ func (list *List) Values() []interface{} {
 	return newElements
 }
 
+//IndexOf returns index of provided element
+func (list *List) IndexOf(value interface{}) int{
+	if list.size == 0 {
+		return -1
+	}
+		for index, element := range list.elements {
+			if element == value {
+				return index
+			}
+		}
+		return -1
+}
 // Empty returns true if list does not contain any elements.
 func (list *List) Empty() bool {
 	return list.size == 0

lists/arraylist/arraylist_test.go

@@ -6,8 +6,9 @@ package arraylist
 
 import (
 	"fmt"
-	"github.com/emirpasic/gods/utils"
 	"testing"
+
+	"github.com/emirpasic/gods/utils"
 )
 
 func TestListAdd(t *testing.T) {
@@ -25,6 +26,33 @@ func TestListAdd(t *testing.T) {
 	}
 }
 
+func TestListIndexOf(t *testing.T) {
+	list := New()
+
+	expectedIndex := -1
+	if index  := list.IndexOf("a"); index != expectedIndex{
+		t.Errorf("Got %v expected %v",index,expectedIndex)
+	}
+
+	list.Add("a")
+	list.Add("b", "c")
+
+	expectedIndex = 0
+	if index  := list.IndexOf("a"); index != expectedIndex{
+		t.Errorf("Got %v expected %v",index,expectedIndex)
+	}
+
+	expectedIndex = 1
+	if index  := list.IndexOf("b"); index != expectedIndex{
+		t.Errorf("Got %v expected %v",index,expectedIndex)
+	}
+
+	expectedIndex = 2
+	if index  := list.IndexOf("c"); index != expectedIndex{
+		t.Errorf("Got %v expected %v",index,expectedIndex)
+	}
+}
+
 func TestListRemove(t *testing.T) {
 	list := New()
 	list.Add("a")