A SpannableStringBuilder used, in this case, to bold parts of a result while typing in a search field.

SpannableStringBuilderActivity.java

// ...

final String contactName = this.contact.getFullname();
final SpannableStringBuilder spannableStringBuilder = new SpannableStringBuilder(contactName);
final StyleSpan boldSpan = new StyleSpan(android.graphics.Typeface.BOLD);
if (!TextUtils.isEmpty(searchTerm) && contactName.toLowerCase().contains(searchTerm.toLowerCase())) {
     int startIndex = contactName.toLowerCase().indexOf(searchTerm.toLowerCase());
     int endIndex = startIndex + searchTerm.length();
     spannableStringBuilder.setSpan(boldSpan, startIndex, endIndex, Spannable.SPAN_INCLUSIVE_INCLUSIVE);
     this.fullname.setText(spannableStringBuilder);
} else {
     this.fullname.setText(contactName);
}

// ...