先来看看AbnfParser类如何对ABNF文法中最简单的一些单字节符号如何进行解析，这些单字节符号包括跳格、换行、回车和空格：

/*    This file is one of the component a Context-free Grammar Parser Generator,    which accept a piece of text as the input, and generates a parser    for the inputted context-free grammar.    Copyright (C) 2013, Junbiao Pan (Email: panjunbiao@gmail.com)    This program is free software: you can redistribute it and/or modify    it under the terms of the GNU General Public License as published by    the Free Software Foundation, either version 3 of the License, or    any later version.    This program is distributed in the hope that it will be useful,    but WITHOUT ANY WARRANTY; without even the implied warranty of    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the    GNU General Public License for more details.    You should have received a copy of the GNU General Public License    along with this program.  If not, see 
    . *///  HTAB           =  %x09	protected String HTAB() throws IOException, MatchException {//      断言下一个字符为0x09（否则抛出MatchException异常）        assertMatch(is.peek(), 0x09);        int value = is.read();//      返回HTAB的字符串值        return String.valueOf((char)value);	}//  LF             =  %x0A	protected String LF() throws IOException, MatchException {//      断言下一个字符为0x0A（否则抛出MatchException异常）        assertMatch(is.peek(), 0x0A);        int value = is.read();//      返回换行的字符串值        return String.valueOf((char)value);	}//  CR             =  %x0D	protected String CR() throws IOException, MatchException {//      断言下一个字符为0x0D（否则抛出MatchException异常）        assertMatch(is.peek(), 0x0D);        int value = is.read();//      返回回车的字符串值        return String.valueOf((char)value);	}//  SP             =  %x20	protected String SP() throws IOException, MatchException {//      断言下一个字符为0x20（否则抛出MatchException异常）        assertMatch(is.peek(), 0x20);        int value = is.read();//      返回空格的字符串值        return String.valueOf((char)value);	}

这些单字符的解析函数不需要向前看（预测），因为当他们一旦被调用，就意味着必须是相应的字符，否则就是抛出异常了。

接下来看看上面各个函数对应的单元测试函数。

/*    This file is one of the component a Context-free Grammar Parser Generator,    which accept a piece of text as the input, and generates a parser    for the inputted context-free grammar.    Copyright (C) 2013, Junbiao Pan (Email: panjunbiao@gmail.com)    This program is free software: you can redistribute it and/or modify    it under the terms of the GNU General Public License as published by    the Free Software Foundation, either version 3 of the License, or    any later version.    This program is distributed in the hope that it will be useful,    but WITHOUT ANY WARRANTY; without even the implied warranty of    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the    GNU General Public License for more details.    You should have received a copy of the GNU General Public License    along with this program.  If not, see 
    . */    //  HTAB           =  %x09    @Test    public void testHTAB() throws Exception {        Tester
    
      tester = new Tester
     
      () {            @Override            public String test(AbnfParser parser) throws MatchException, IOException {//              测试器负责调用被测函数AbnfParser.HTAB()                return parser.HTAB();            }        };//      测试用例1:一个0x09字符输入的情形        Assert.assertEquals(String.valueOf((char)0x09), AbnfParserFactory.newInstance(new char[] {0x09}).HTAB());//      测试用例2:两个0x09字符输入的情形        Assert.assertEquals(String.valueOf((char) 0x09), AbnfParserFactory.newInstance(new char[]{0x09, 0x09}).HTAB());//      测试用例3:一个0x0D字符输入的情形（异常）        Assertion.assertMatchException("" + (char) 0x0D, tester, 1, 1);//      测试用例3:空字符输入的情形（异常）        Assertion.assertMatchException("", tester, 1, 1);    }    //  LF             =  %x0A    @Test    public void testLF() throws Exception {        Tester
      
        tester = new Tester
       
        () {            @Override            public String test(AbnfParser parser) throws MatchException, IOException {//              测试器负责调用被测函数AbnfParser.LF()                return parser.LF();            }        };//      测试用例1:一个0x0A字符输入的情形        Assert.assertEquals(String.valueOf((char)0x0A), AbnfParserFactory.newInstance(new char[] {0x0A}).LF());//      测试用例2:两个0x0A字符输入的情形        Assert.assertEquals(String.valueOf((char) 0x0A), AbnfParserFactory.newInstance(new char[]{0x0A, 0x0A}).LF());//      测试用例3:一个0x0D字符输入的情形（异常）        Assertion.assertMatchException("", tester, 1, 1);//      测试用例3:空字符输入的情形（异常）        Assertion.assertMatchException("" + (char)0x0D, tester, 1, 1);    }    //  CR             =  %x0D    @Test    public void testCR() throws Exception {        Tester
        
          tester = new Tester
         
          () { @Override public String test(AbnfParser parser) throws MatchException, IOException { return parser.CR(); } }; Assert.assertEquals(String.valueOf((char) 0x0D), AbnfParserFactory.newInstance(new char[]{0x0D, 0x0D}).CR()); Assertion.assertMatchException("", tester, 1, 1); Assertion.assertMatchException("" + (char)0x0A, tester, 1, 1); } // SP = %x20 @Test public void testSP() throws Exception { Tester
          
            tester = new Tester
           
            () { @Override public String test(AbnfParser parser) throws MatchException, IOException { return parser.SP(); } }; Assert.assertEquals(String.valueOf((char)0x20), AbnfParserFactory.newInstance(new char[] {0x20, 0x20}).SP()); Assertion.assertMatchException("", tester, 1, 1); Assertion.assertMatchException("" + (char)0x0D, tester, 1, 1); }