Refactor compareLong method using Long.compare, corrected the local variable name (#1136)

Author: harikrishna553

webmagic-core/src/main/java/us/codecraft/webmagic/utils/NumberUtils.java

@@ -6,12 +6,6 @@
 public abstract class NumberUtils {
 
     public static int compareLong(long o1, long o2) {
-        if (o1 < o2) {
-            return -1;
-        } else if (o1 == o2) {
-            return 0;
-        } else {
-            return 1;
-        }
+    	return Long.compare(o1, o2);
     }
 }

webmagic-core/src/main/java/us/codecraft/webmagic/utils/WMCollections.java

@@ -21,10 +21,10 @@ public static <T> Set<T> newHashSet(T... t){
     }
 
     public static <T> List<T> newArrayList(T... t){
-        List<T> set = new ArrayList<T>(t.length);
+        List<T> list = new ArrayList<T>(t.length);
         for (T t1 : t) {
-            set.add(t1);
+            list.add(t1);
         }
-        return set;
+        return list;
     }
 }