refactor 454

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_454.java

@@ -5,24 +5,20 @@
 
 public class _454 {
     public static class Solution1 {
-        public int fourSumCount(int[] A, int[] B, int[] C, int[] D) {
+        public int fourSumCount(int[] nums1, int[] nums2, int[] nums3, int[] nums4) {
             Map<Integer, Integer> map = new HashMap();
             int result = 0;
-            int len = A.length;
+            int len = nums1.length;
             for (int i = 0; i < len; i++) {
                 for (int j = 0; j < len; j++) {
-                    int sum = A[i] + B[j];
-                    if (map.containsKey(sum)) {
-                        map.put(sum, map.get(sum) + 1);
-                    } else {
-                        map.put(sum, 1);
-                    }
+                    int sum = nums1[i] + nums2[j];
+                    map.put(sum, map.getOrDefault(sum, 0) + 1);
                 }
             }
 
             for (int i = 0; i < len; i++) {
                 for (int j = 0; j < len; j++) {
-                    int sum = -(C[i] + D[j]);
+                    int sum = -(nums3[i] + nums4[j]);
                     if (map.containsKey(sum)) {
                         result += map.get(sum);
                     }