Add Optimal String Reversal Solution

JAVA/reverseString.java

@@ -1,17 +1,28 @@
-public class reverseString
-{    
-    public static void main(String[] args) {    
-        String string = "Dream big";    
-
-        String reversedStr = "";    
-
-
-        for(int i = string.length()-1; i >= 0; i--){    
-            reversedStr = reversedStr + string.charAt(i);    
-        }    
-
-        System.out.println("Original string: " + string);    
-
-        System.out.println("Reverse of given string: " + reversedStr);    
-    }    
-}    
+public class reverseString {
+    public static String reverse(String str) {
+        // converting str to char array for easy traversal
+        char[] chars = str.toCharArray();
+        //pointing one pointer to left
+        int left = 0;
+        //pointing another pointer to right
+        int right = chars.length - 1;
+        // moving till left and right not crosses each other
+        while (left < right) {
+            // swaping of left and right to reverse a string
+            char temp = chars[left];
+            chars[left] = chars[right];
+            chars[right] = temp;
+            left++;
+            right--;
+        }
+
+        return new String(chars);
+    }
+
+    public static void main(String args[]){
+       String str="Dream big"; // Changed the input string
+       //calling the function which will return a string so we are printing that
+       System.out.println(reverse(str));
+    }
+}
+