Can anyone help with amending the below code so that it returns the value in UPPER case?

postcodenum = postcode.getAlphaNumeric().removeAllAlpha();

getlastnum = postcodenum.subText(postcodenum.length() - 1,postcodenum.length());

newvalue = " " + getlastnum;

lastindex = postcode.lastIndexOf(getlastnum);

newstr = postcode.subText(0,lastindex) + " " + postcode.subText(lastindex,postcode.length());

mp = Map();

mp.put("Post_Code",newstr);

update = zoho.crm.updateRecord("Affordability",leadid.toLong(),mp);

info mp;

info update;