Try this: // given double myDouble...
NumberFormat numFmt = NumberFormat.getNumberInstance() ;
numFmt.setMaximumFractionDigits(1) ;
numFmt.setMinimumFractionDigits(1) ;
String myDoubleStr = numFmt.format(myDouble) ;
note: For most locales, NumberFormat.getNumberInstance() returns a DecimalFormat object.