add a solution for 709

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_709.java

@@ -1,9 +1,32 @@
 package com.fishercoder.solutions;
 
+import java.util.HashMap;
+import java.util.Map;
+
 public class _709 {
     public static class Solution1 {
-        public String toLowerCase(String str) {
-            return str.toLowerCase();
+        public String toLowerCase(String s) {
+            return s.toLowerCase();
+        }
+    }
+
+    public static class Solution2 {
+        public String toLowerCase(String s) {
+            Map<Character, Character> map = new HashMap<>();
+            String upper = new String("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
+            String lower = new String("abcdefghijklmnopqrstuvwxyz");
+            for (int i = 0; i < upper.length(); i++) {
+                map.put(upper.charAt(i), lower.charAt(i));
+            }
+            StringBuilder sb = new StringBuilder();
+            for (int i = 0; i < s.length(); i++) {
+                if (map.containsKey(s.charAt(i))) {
+                    sb.append(map.get(s.charAt(i)));
+                } else {
+                    sb.append(s.charAt(i));
+                }
+            }
+            return sb.toString();
         }
     }
 }