Can someone please solve this for me? using java programming

(a) Complete the Java code fragment below so that string rev will contain the reverse of str. which is read from the command line. Use the two String methods substring() and length() only String st = rev = for (b) How many String objects are created in the for loop of your code in part (a) if string str is "test"? Justify your answer (c) Which String method is better than substring() in part (a)? Why