增加java版本---分割平衡字符串

Add java implementation

problems/1221.分割平衡字符串.md

@@ -93,6 +93,18 @@ public:
 ## Java
 
 ```java
+class Solution {
+    public int balancedStringSplit(String s) {
+        int result = 0;
+        int count = 0;
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == 'R') count++;
+            else count--;
+            if (count == 0) result++;
+        }
+        return result;
+    }  
+}
 ```
 
 ## Python