Create Number-of-Good-Pairs.java & Update README.md (#138)

* Create Number-of-Good-Pairs.java

* Update README.md

Author: MatthewWurl

Java/Number-of-Good-Pairs.java

@@ -0,0 +1,14 @@
+class Solution {
+    public int numIdenticalPairs(int[] nums) {
+        int numGoodPairs = 0;
+        
+        for (int i = 0; i < nums.length; i++) {
+            for (int j = 0; j < nums.length; j++) {
+                if (i == j) continue; // cannot check against itself
+                if (nums[i] == nums[j] && i < j) numGoodPairs++;
+            }
+        }
+        
+        return numGoodPairs;
+    }
+}

README.md

@@ -140,6 +140,7 @@ Check out ---> [Sample PR](https://github.com/codedecks-in/LeetCode-Solutions/pu
 | 283     | [Move-Zeroes](https://leetcode.com/problems/move-zeroes/)                                                                     | [C++](./C++/Move-Zeroes.cpp)                                                                                      | O(N)         | O(1)          | Easy       | Array              |
 | 27     | [Remove-Element](https://leetcode.com/problems/remove-element/)                                                                     | [C++](./C++/remove-element.cpp)                                                                                      | O(N)         | O(1)          | Easy       | Array              |
 | 36     | [Valid Sudoku](https://leetcode.com/problems/valid-sudoku/)                                                                     | [Java](./Java/valid-sudoku.java)                                                                                      | O(N^2)         | O(N)          | Medium       | Array, 2D Matrix              |
+| 1512   | [Number of Good Pairs](https://leetcode.com/problems/number-of-good-pairs/)                                                                     | [Java](./Java/Number-of-Good-Pairs.java)                                                                                      | O(N^2)         | O(1)          | Easy       | Array              |
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