I have been making more use of CharSequence in text processing to avoid unnecessary generating Strings.

A trivial example is.
public CharSequence cut(CharSequence str, int len) {
if (str.length <= len)
return;
StringBuilder ret = new StringBuilder(len);
ret.append(str.subSequence(0, len-3));
ret.append("...");
return ret;
}

This result can be used in a StringBuilder, or be passed to a method which requires a String.
e.g.
public void setDescription(String description) { ... }

setDescription(cut(longDescription, MAX_LENGTH));

One of the options is to cast to String.

setDescription((String) cut(longDescription, MAX_LENGTH));

This may work some of the time, but a better, possiblily more reliable suggestion is call toString()

setDescription(cut(longDescription, MAX_LENGTH).toString());

I believe calling toString() may be a better way convert in a wide range of situations.