%%
%% This is file `example-CJKchecksingle.tex',
%% generated with the docstrip utility.
%%
%% The original source files were:
%%
%% xeCJK.dtx  (with options: `example-CJKchecksingle')
%% 
%%  Version 2.3.10 (30-Sept-2009)
%% 
%%  Copyright (C) Wenchang Sun <sunwch@hotmail.com>
%% 
%%  This file may be distributed and/or modified under the
%%  conditions of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%%  The latest version of this license is in
%%    http://www.latex-project.org/lppl.txt
%%  and version 1.3 or later is part of all distributions of LaTeX
%%  version 2005/12/01 or later.
%% 
\documentclass{article}
\usepackage[boldfont,slantfont,CJKaddspaces,CJKchecksingle]{xeCJK}
\setCJKmainfont{AR PL SungtiL GB}
\textwidth 120mm
\oddsidemargin 0pt
\def\usemacro#1{\csname#1\endcsname $\backslash$#1}
\begin{document}
\baselineskip 18pt
\parskip 10pt
\parindent 0em

\long\def\sometexts{xeCJK   改进了中英文间距的处理，并可以避免单个汉字独占一段的最后一行。

xeCJK  改进了中英文间距的处理，并且可以避免单个汉字独占一段的最后一行。

xeCJK  改进了中英文间距的处理, 并且还可以避免单个汉字独占一段的最后一行.

}

\sometexts
\vskip 20mm

不用CJKchecksingle的效果：

\makeatletter
\def\xeCJK@i@i{\CJKglue\CJKsymbol}
\sometexts
\end{document}

\endinput
%%
%% End of file `example-CJKchecksingle.tex'.
