Reversing a string is easy. One way is to read a string character by character in reverse order and concatenate it with a string - lets say reversedString.
Easy and efficient is to use reverse() method of StringBuffer.
String a = "French is a difficult language.";
System.out.println("Original string: " + a);
StringBuffer b = new StringBuffer(a).reverse();
System.out.println("Reversed string: " + b);