提取重构

Author: timandy

src/main/java/com/bestvike/linq/enumerable/ToCollection.java

@@ -6,7 +6,6 @@
 import com.bestvike.linq.IEnumerable;
 import com.bestvike.linq.exception.Errors;
 
-import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -55,15 +54,7 @@ public static <TSource> List<TSource> toList(IEnumerable<TSource> source) {
             return listProvider._toList();
         }
 
-        if (source instanceof ICollection) {
-            ICollection<TSource> collection = (ICollection<TSource>) source;
-            return collection._toList();
-        }
-
-        List<TSource> list = new ArrayList<>();
-        for (TSource item : source)
-            list.add(item);
-        return list;
+        return EnumerableHelpers.toList(source);
     }
 
     public static <TSource, TKey> Map<TKey, TSource> toMap(IEnumerable<TSource> source, Func1<TSource, TKey> keySelector) {

src/main/java/com/bestvike/linq/enumerable/__EnumerableHelpers.java

@@ -4,8 +4,12 @@
 import com.bestvike.linq.IEnumerable;
 import com.bestvike.linq.IEnumerator;
 import com.bestvike.linq.util.ArrayUtils;
+import com.bestvike.linq.util.ListUtils;
 import com.bestvike.out;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * Created by 许崇雷 on 2018-05-07.
  */
@@ -150,4 +154,22 @@ public static <T> Object[] toArray(IEnumerable<T> source, out<Integer> length) {
         length.value = 0;
         return ArrayUtils.empty();
     }
+
+    //Converts an enumerable to an list.
+    public static <T> List<T> toList(IEnumerable<T> source) {
+        assert source != null;
+
+        if (source instanceof ICollection) {
+            ICollection<T> collection = (ICollection<T>) source;
+            int count = collection._getCount();
+            return count == 0 ? ListUtils.empty() : collection._toList();
+        }
+
+        List<T> list = new ArrayList<>();
+        try (IEnumerator<T> e = source.enumerator()) {
+            while (e.moveNext())
+                list.add(e.current());
+        }
+        return list;
+    }
 }