Java code to process special characters that need to be replaced by other special characters

I am writing Java code to process a string received from a Mainframe that contains special characters that need to be replaced by other special characters, my search characters are §ÄÖÜäüßö@[\]~{¦} and the replacement characters are @[\]{}~¦§ÄÖÜßäöü so if the string has a { in it I need to replace it with ä and example of my input is "0.201322.05.2017LM-R{der Dopp"

My code currently is

        String repChar = "§ÄÖÜäüßö@[\\\\]~{¦}@[\\\\]{}~¦§ÄÖÜßäöü";
        // Split String and Convert
        String repCharin = repChar.substring(0, repChar.length()/2-1);
        String repCharout = repChar.substring(repChar.length()/2, repChar.length()-1);          
        String strblob = new String(utf8ContentIn);
        // Convert  
        for (int j=0; j < repCharin.length();j++) {
            strblob = strblob.replace(repCharin.substring(j, 1), repCharout.substring(j, 1));                               
        }
        byte [] utf8Content = strblob.getBytes();

But it generates the following error

java.lang.StringIndexOutOfBoundsException at java.lang.String.substring(String.java:1240)

The \\ are escaped characters I only need a single \