I believe this is the answer to the question you're asking.
You're looking for the concat method.
For instance:
String concatenatedString = new String().concat(string1+" "+string2);
Alternatively:
String string1 = "This";
String string2 = "is a concatenated string";
string1 = string1.concat(" " + string2);
string1 would now be "This is a concatenated string"
I believe in your instance you would want to do:
String from = new String().concat(TaskTable.COLUMN_DESCRIPTION + " " + TaskTable.COLUMN_DATE);