语法分析器实现过程（java）

语法分析器是编译原理的一个实验，本文将会详细给出实现的具体步骤，利用java进行示例讲解，完整源码可在 https://download.csdn.net/download/_/ 下载。

一、实验目的

设计、编写一个语法分析程序，加深对语法分析原理的理解。

二、实验原理

语法分析器是在词法分析之后，根据词法分析的结果和定义的语法规则判断输入的程序是否有语法错误，LL(1)分析是使用显式栈而不是递归调用来完成分析。以标准方式表示这个栈非常有用，这样LL(1)分析程序的动作就可以快捷地显现出来。LL(1)的含义是：第一个L表明自顶向下分析是从左向右扫描输入串，第2个L表明分析过程中将使用最左推导，1表明只需向右看一个符号便可决定如何推导，即选择哪个产生式(规则)进行推导。

三、实验内容

四、实验方法

五、实验设计

1.定义语法分析使用的文法语言：

<程序>
::=
<语句>
<程序>
| Ɛ;


<语句>
::=
<变量定义语句>
|
<赋值语句>
|
<函数调用语句>
|


|
<循环语句>
| Ɛ


<变量定义语句>
::=
<变量类型>
<标识符表>
;


<赋值语句>
::=
<标识符>
=
<表达式>
;


<函数调用语句>
::=
<标识符>
(
<标识符表>
);



::= if (
<条件表达式>
) {
<语句>
}




::= else{
<语句>
} | Ɛ


<循环语句>
::= while (
<条件表达式>
) {
<语句>
}


<标识符表>
::=
<标识符>
|
<标识符表>
,
<标识符>


<条件表达式>
::=
<表达式>
<比较运算符>
<表达式>


<比较运算符>
::= > | >= | < | <= | != | ==

<变量类型>
::= char | short | int | long | float | double


<表达式>
::= +T | -T | T |
<表达式>
+ T |
<表达式>
-T

T ::= F | T*F | T/F
F ::=
<标识符>
|
<无符号整数>
| (
<表达式>
)

2.将上述文法用产生式表示：

3.提取公共左因子：

4.消除左递归：

5.求FIRST集：

6.求FOLLOW集：

7.构造LL(1)的预测分析表：

LL（1）预测分析表中的数字分别代表的产生式如下：
0：S → A L;
1：S → id B
2：S → if(X){P}Q
3：S → while(X){P}
4：S → Ɛ
5：B → (L);
6：B → =E;
7：L → id L’
8：L’→ ,id L’
9：L’→ Ɛ
10：Q → else{S}
11：Q → Ɛ
12：X → ERE
13：E → +TE’
14：E → -TE’
15：E → TE’
16：E’→ ME’
17：E’→ Ɛ
18：M → +T
19：M → -T
20：T → FT’
21：T’→ NT’
22：T’→ Ɛ
23：N → *F
24：N → /F
25：F → id
26：F → num
27：F → (E)
28：R → >
29：R → >=
30：R → <
31：R → <=
32：R → ==
33：R → !=
34：S’ → S S’
35：S’ → Ɛ
36：A → char
37：A → short
38：A → int
39：A → long
40：A → float
41：A → double

六、数据结构

七、实现代码

1.初始化

首先定义了五个全局变量：

private static ArrayList<String> stack = new ArrayList<>(); // 当前栈 private static ArrayList<Integer> reader = new ArrayList<>(); // 待读队列 private static Production[] productions = new Production[42]; // 产生式数组 private static HashMap<Integer, String> map_i2s; // 种别码Map，种别码为键，单词为值 private static HashMap<String, Integer> map_s2i; // 种别码Map，单词为键，种别码为值 

初始化种别码Map，要和词法分析器内单词对应的种别码相同：

private static void initMap() { 
    map_s2i = new HashMap<>(); map_s2i.put("char", 1); map_s2i.put("short", 2); map_s2i.put("int", 3); map_s2i.put("long", 4); map_s2i.put("float", 5); map_s2i.put("double", 6); map_s2i.put("final", 7); map_s2i.put("static", 8); map_s2i.put("if", 9); map_s2i.put("else", 10); map_s2i.put("while", 11); map_s2i.put("do", 12); map_s2i.put("for", 13); map_s2i.put("break", 14); map_s2i.put("continue", 15); map_s2i.put("void", 16); map_s2i.put("id", 20); map_s2i.put("num", 30); map_s2i.put("=", 31); map_s2i.put("==", 32); map_s2i.put(">", 33); map_s2i.put("<", 34); map_s2i.put(">=", 35); map_s2i.put("<=", 36); map_s2i.put("+", 37); map_s2i.put("-", 38); map_s2i.put("*", 39); map_s2i.put("/", 40); map_s2i.put("(", 41); map_s2i.put(")", 42); map_s2i.put("[", 43); map_s2i.put("]", 44); map_s2i.put("{", 45); map_s2i.put("}", 46); map_s2i.put(",", 47); map_s2i.put(":", 48); map_s2i.put(";", 49); map_s2i.put("!=", 50); map_s2i.put("$", 60); map_i2s = new HashMap<>(); map_i2s.put(1, "char"); map_i2s.put(2, "short"); map_i2s.put(3, "int"); map_i2s.put(4, "long"); map_i2s.put(5, "float"); map_i2s.put(6, "double"); map_i2s.put(7, "final"); map_i2s.put(8, "static"); map_i2s.put(9, "if"); map_i2s.put(10, "else"); map_i2s.put(11, "while"); map_i2s.put(12, "do"); map_i2s.put(13, "for"); map_i2s.put(14, "break"); map_i2s.put(15, "continue"); map_i2s.put(16, "void"); map_i2s.put(20, "id"); map_i2s.put(30, "num"); map_i2s.put(31, "="); map_i2s.put(32, "=="); map_i2s.put(33, ">"); map_i2s.put(34, "<"); map_i2s.put(35, ">="); map_i2s.put(36, "<="); map_i2s.put(37, "+"); map_i2s.put(38, "-"); map_i2s.put(39, "*"); map_i2s.put(40, "/"); map_i2s.put(41, "("); map_i2s.put(42, ")"); map_i2s.put(43, "["); map_i2s.put(44, "]"); map_i2s.put(45, "{"); map_i2s.put(46, "}"); map_i2s.put(47, ","); map_i2s.put(48, ":"); map_i2s.put(49, ";"); map_i2s.put(50, "!="); map_i2s.put(60, "$"); } 

初始化产生式：规则自己定义

/ * 产生式类 */ private static class Production { 
    String l_str; String[] r_str; String prod; public Production(String l_str, String[] r_str, String prod) { 
    this.l_str = l_str; this.r_str = r_str; this.prod = prod; } } private static void initProductions() { 
    productions[0] = new Production("S", new String[]{ 
   "A", "L", String.valueOf(map_s2i.get(";"))}, "S --> A L;"); productions[1] = new Production("S", new String[]{ 
   String.valueOf(map_s2i.get("id")), "B"}, "S --> id B"); productions[2] = new Production("S", new String[]{ 
   String.valueOf(map_s2i.get("if")), String.valueOf(map_s2i.get("(")), "X", String.valueOf(map_s2i.get(")")), String.valueOf(map_s2i.get("{")), "S", String.valueOf(map_s2i.get("}")), "Q"}, "S --> if(X){S}Q"); productions[3] = new Production("S", new String[]{ 
   String.valueOf(map_s2i.get("while")), String.valueOf(map_s2i.get("(")), "X", String.valueOf(map_s2i.get(")")), String.valueOf(map_s2i.get("{")), "S", String.valueOf(map_s2i.get("}"))}, "S --> while(X){S}"); productions[4] = new Production("S", new String[]{ 
   "ε"}, "S --> ε"); productions[5] = new Production("B", new String[]{ 
   String.valueOf(map_s2i.get("(")), "L", String.valueOf(map_s2i.get(")")), String.valueOf(map_s2i.get(";"))}, "B --> (L);"); productions[6] = new Production("B", new String[]{ 
   String.valueOf(map_s2i.get("=")), "E", String.valueOf(map_s2i.get(";"))}, "B --> =E;"); productions[7] = new Production("L", new String[]{ 
   String.valueOf(map_s2i.get("id")), "L'"}, "L --> id L'"); productions[8] = new Production("L'", new String[]{ 
   String.valueOf(map_s2i.get(",")), String.valueOf(map_s2i.get("id")), "L'"}, "L' --> ,id L'"); productions[9] = new Production("L'", new String[]{ 
   "ε"}, "L' --> ε"); productions[10] = new Production("Q", new String[]{ 
   String.valueOf(map_s2i.get("else")), String.valueOf(map_s2i.get("{")), "S", String.valueOf(map_s2i.get("}"))}, "Q --> else{S}"); productions[11] = new Production("Q", new String[]{ 
   "ε"}, "Q --> ε"); productions[12] = new Production("X", new String[]{ 
   "E", "R", "E"}, "X --> ERE"); productions[13] = new Production("E", new String[]{ 
   String.valueOf(map_s2i.get("+")), "T", "E'"}, "E --> +TE'"); productions[14] = new Production("E", new String[]{ 
   String.valueOf(map_s2i.get("-")), "T", "E'"}, "E --> -TE'"); productions[15] = new Production("E", new String[]{ 
   "T", "E'"}, "E --> TE'"); productions[16] = new Production("E'", new String[]{ 
   "M", "E'"}, "E' --> ME'"); productions[17] = new Production("E'", new String[]{ 
   "ε"}, "E' --> ε"); productions[18] = new Production("M", new String[]{ 
   String.valueOf(map_s2i.get("+")), "T"}, "M --> +T"); productions[19] = new Production("M", new String[]{ 
   String.valueOf(map_s2i.get("-")), "T"}, "M --> -T"); productions[20] = new Production("T", new String[]{ 
   "F", "T'"}, "T --> FT'"); productions[21] = new Production("T'", new String[]{ 
   "N", "T'"}, "T' --> NT'"); productions[22] = new Production("T'", new String[]{ 
   "ε"}, "T' --> ε"); productions[23] = new Production("N", new String[]{ 
   String.valueOf(map_s2i.get("*")), "F"}, "N --> *F"); productions[24] = new Production("N", new String[]{ 
   String.valueOf(map_s2i.get("/")), "F"}, "N --> /F"); productions[25] = new Production("F", new String[]{ 
   String.valueOf(map_s2i.get("id"))}, "F --> id"); productions[26] = new Production("F", new String[]{ 
   String.valueOf(map_s2i.get("num"))}, "F --> num"); productions[27] = new Production("F", new String[]{ 
   String.valueOf(map_s2i.get("(")), "E", String.valueOf(map_s2i.get(")"))}, "F --> (E)"); productions[28] = new Production("R", new String[]{ 
   String.valueOf(map_s2i.get(">"))}, "R --> >"); productions[29] = new Production("R", new String[]{ 
   String.valueOf(map_s2i.get(">="))}, "R --> >="); productions[30] = new Production("R", new String[]{ 
   String.valueOf(map_s2i.get("<"))}, "R --> <"); productions[31] = new Production("R", new String[]{ 
   String.valueOf(map_s2i.get("<="))}, "R --> <="); productions[32] = new Production("R", new String[]{ 
   String.valueOf(map_s2i.get("=="))}, "R --> =="); productions[33] = new Production("R", new String[]{ 
   String.valueOf(map_s2i.get("!="))}, "R --> !="); productions[34] = new Production("S'", new String[]{ 
   "S", "S'"}, "S' --> SS'"); productions[35] = new Production("S'", new String[]{ 
   "ε"}, "S' --> ε"); productions[36] = new Production("A", new String[]{ 
   String.valueOf(map_s2i.get("char"))}, "A --> char"); productions[37] = new Production("A", new String[]{ 
   String.valueOf(map_s2i.get("short"))}, "A --> short"); productions[38] = new Production("A", new String[]{ 
   String.valueOf(map_s2i.get("int"))}, "A --> int"); productions[39] = new Production("A", new String[]{ 
   String.valueOf(map_s2i.get("long"))}, "A --> long"); productions[40] = new Production("A'", new String[]{ 
   String.valueOf(map_s2i.get("float"))}, "A --> float"); productions[41] = new Production("A", new String[]{ 
   String.valueOf(map_s2i.get("double"))}, "A --> double"); } 

main()函数的部分：

int stackTop = 1; int readerTop = 0; int index = 0; // 当前步骤数 initMap(); // 初始化种别码Map initProductions(); // 产生式初始化 stack.add(0, String.valueOf(map_s2i.get("$"))); // 在stack底部加上$ stack.add(stackTop, "S'"); // 将S'压入栈 

2.读入词法分析结果

System.out.print("请输入词法分析结果的文件路径："); Scanner scanner = new Scanner(System.in); String filepath = scanner.next(); StringBuffer outputBuffer = new StringBuffer(); // 输出到文件的StringBuffer // 通过词法分析器的输出结果，初始化reader try { 
    readToReader(filepath); } catch (IOException e) { 
    e.printStackTrace(); } reader.add(map_s2i.get("$")); // 在reader末尾加上$ public static void readToReader(String filePath) throws IOException { 
    InputStream is = new FileInputStream(filePath); String line; // 用来保存每行读取的内容 BufferedReader br = new BufferedReader(new InputStreamReader(is)); line = br.readLine(); // 读取第一行 while (line != null) { 
    // 如果 line 为空说明读完了 int pos = line.indexOf(","); reader.add(Integer.valueOf(line.substring(0, pos))); line = br.readLine(); // 读取下一行 } br.close(); is.close(); } 

注意到我们在stack和reader末尾都添加了$，当两者的$匹配时表示语法分析结束。

3.语法分析

main()函数部分：

while (stackTop >= 0) { 
    System.out.printf("%-6s", "第" + ++index + "步："); System.out.printf("%-10s", "当前栈："); outputBuffer.append("第" + index + "步： 当前栈："); StringBuffer sb = new StringBuffer(); // 引入StringBuffer仅为控制在控制台的输出格式对齐 for (int i = 0; i <= stackTop; i++) { 
    String str = null; try { 
    str = map_i2s.get(Integer.valueOf(stack.get(i))); if (str != null) { 
    sb.append(str + " "); outputBuffer.append(str + " "); } } catch (NumberFormatException e) { 
    sb.append(stack.get(i) + " "); outputBuffer.append(stack.get(i) + " "); } } System.out.printf("%-30s", sb.toString()); System.out.print("待读队列："); outputBuffer.append(" 待读队列："); sb = new StringBuffer(); for (int i = 0; i < reader.size(); i++) { 
    sb.append(map_i2s.get(reader.get(i)) + " "); outputBuffer.append(map_i2s.get(reader.get(i)) + " "); } System.out.printf("%-55s", sb.toString()); if (match(stackTop, readerTop)) { 
    stackTop--; System.out.print("\n"); outputBuffer.append("\n"); } else { 
    int i = ll1_table(stackTop, readerTop); stackTop += stackPush(stackTop, productions[i]); // 压栈 System.out.printf("%-30s", "下一步所用产生式：" + productions[i].prod); System.out.println(); outputBuffer.append(" 下一步所用产生式：" + productions[i].prod + "\n"); } } if (stackTop == -1) { 
    System.out.println("语法分析成功"); outputBuffer.append("Accept"); } 

检测reader头部和stack顶部是否匹配，返回匹配结果

private static boolean match(int stackTop, int readerTop) { 
    try { 
    int stackTopVal = Integer.valueOf(stack.get(stackTop)); // 未抛出异常说明是终结符 if (stackTopVal == reader.get(0)) { 
    stack.remove(stackTop); reader.remove(readerTop); return true; } else { 
    return false; } } catch (NumberFormatException e) { 
    // 抛出异常说明是非终结符 return false; } } 

利用LL(1)预测分析表进行分析，返回单词种别码。

private static int ll1_table(int stackTop, int readerTop) { 
    if ("S".equals(stack.get(stackTop))) { 
    if ("char".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 0; } else if ("short".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 0; } else if ("int".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 0; } else if ("long".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 0; } else if ("float".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 0; } else if ("double".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 0; } else if ("id".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 1; } else if ("if".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 2; } else if ("while".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 3; } else if ("}".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 4; } else if ("$".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 4; } else { 
    return -1; } } else if ("B".equals(stack.get(stackTop))) { 
    if ("(".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 5; } else if ("=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 6; } else { 
    return -1; } } else if ("L".equals(stack.get(stackTop))) { 
    if ("id".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 7; } else { 
    return -1; } } else if ("L'".equals(stack.get(stackTop))) { 
    if (";".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 9; } else if (")".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 9; } else if ("}".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 9; } else if ("$".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 9; } else if (",".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 8; } else { 
    return -1; } } else if ("Q".equals(stack.get(stackTop))) { 
    if ("}".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 11; } else if ("$".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 11; } else if ("else".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 10; } else { 
    return -1; } } else if ("X".equals(stack.get(stackTop))) { 
    if ("id".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 12; } else if ("num".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 12; } else if ("+".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 12; } else if ("-".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 12; } else if ("(".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 12; } else { 
    return -1; } } else if ("E".equals(stack.get(stackTop))) { 
    if ("id".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 15; } else if ("num".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 15; } else if ("(".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 15; } else if ("+".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 13; } else if ("-".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 14; } else { 
    return -1; } } else if ("E'".equals(stack.get(stackTop))) { 
    if ("+".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 16; } else if ("-".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 16; } else if (">".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 17; } else if (">=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 17; } else if ("<".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 17; } else if ("<=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 17; } else if ("==".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 17; } else if ("!=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 17; } else if (";".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 17; } else if (")".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 17; } else { 
    return -1; } } else if ("M".equals(stack.get(stackTop))) { 
    if ("+".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 18; } else if ("-".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 19; } else { 
    return -1; } } else if ("T".equals(stack.get(stackTop))) { 
    if ("id".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 20; } else if ("num".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 20; } else if ("(".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 20; } } else if ("T'".equals(stack.get(stackTop))) { 
    if ("+".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if ("-".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if ("*".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 21; } else if ("/".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 21; } else if (">".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if (">=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if ("<".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if ("<=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if ("==".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if ("!=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if (";".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else if (")".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 22; } else { 
    return -1; } } else if ("N".equals(stack.get(stackTop))) { 
    if ("*".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 23; } else if ("/".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 24; } else { 
    return -1; } } else if ("F".equals(stack.get(stackTop))) { 
    if ("id".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 25; } else if ("num".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 26; } else if ("(".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 27; } else { 
    return -1; } } else if ("R".equals(stack.get(stackTop))) { 
    if (">".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 28; } else if (">=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 29; } else if ("<".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 30; } else if ("<=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 31; } else if ("==".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 32; } else if ("!=".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 33; } else { 
    return -1; } } else if ("S'".equals(stack.get(stackTop))) { 
    if ("char".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("short".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("int".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("long".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("float".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("double".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("id".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("if".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("while".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 34; } else if ("$".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 35; } else { 
    return -1; } } else if ("A".equals(stack.get(stackTop))) { 
    if ("char".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 36; } else if ("short".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 37; } else if ("int".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 38; } else if ("long".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 39; } else if ("float".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 40; } else if ("double".equals(map_i2s.get(reader.get(readerTop)))) { 
    return 41; } else { 
    return -1; } } else { 
    System.out.println("语法错误"); } return -1; } 

4.输出结果到文件

System.out.print("请输入语法分析结果文件的保存路径："); String outputPath = scanner.next(); // 将StringBuffer的内容输出到文件 File outputFile = new File(outputPath); if (outputFile.exists()) { 
    outputFile.delete(); } PrintWriter writer = null; try { 
    outputFile.createNewFile(); writer = new PrintWriter(new FileOutputStream(outputFile)); writer.write(outputBuffer.toString()); } catch (IOException e1) { 
    e1.printStackTrace(); } finally { 
    if (writer != null) { 
    writer.close(); } } 

八、运行结果

2019-10-16补充stackPush方法：

private static int stackPush(int stackTop, Production production) { 
     int len = production.r_str.length; stack.remove(stackTop); if ("ε".equals(production.r_str[0])) { 
     } else { 
     for (int i = len - 1; i >= 0; i--) { 
     stack.add(production.r_str[i]); } return len - 1; } return -1; }