词法编辑器(Java)
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import java.awt.*; import java.util.Scanner; /** * Created by s2002 on 2016/9/30. */ public class com { public static void main(String[] args) { //限制字符串最大值 final int MAX_LEN = 100; //关键字 String[] key_word = new String[]{"begin","end","if","then","while","do"}; //录入用户输入 Scanner input = new Scanner(System.in); System.out.print("Please input a string <end with ‘#‘>:"); String uString = input.nextLine(); char[] analyseData = new char[MAX_LEN]; int index = 0, key = 0; List list = new List(); do { String compareStr = null; char temp = uString.charAt(index); list = extactCharacters(temp, analyseData, key_word, uString, index, compareStr); if (list.getItemCount() == 0) { index++; continue; } // 规定List的第一个元素为index,第二个元素为key index = Integer.parseInt(list.getItem(0)); key = Integer.parseInt(list.getItem(1)); String words = list.getItem(2); System.out.println("< " + key + " ," + words + " >"); } while (key != 0); } public static List extactCharacters(char temp, char[] analyseDate, String[] keywords, String uString, int index, String compareStr) { int keyID = -1, m = 0; List list = new List(); //判断下一个读入的字符是否为空格,若读取到空格则跳过,提取下一个字符进行判断 while (temp != ‘ ‘) { //判断当前字符是字母或者数字和字母的组合 if (temp >= ‘a‘ && temp <= ‘z‘) { m = 0; // 当读取到不是大小写字母或者数字时候判断为一个单词读取完成 while (temp >= ‘a‘ && temp <= ‘z‘ || temp >= ‘A‘ && temp <= ‘Z‘ || temp >= ‘0‘ && temp <= ‘9‘) { analyseDate[m++] = temp; compareStr += temp + ""; temp = uString.charAt(++index); } // 与读取出来的字符判断是否为关键字 compareStr = compareStr.substring(4); for (int i = 0; i < 6; i++) { if (compareStr.equals(keywords[i])) { keyID = i + 1; list.add(index + ""); list.add(keyID + ""); list.add(compareStr); return list; } } //若为非关键字就当作为标识符 keyID = 10; list.add(index + ""); list.add(keyID + ""); list.add(compareStr); return list; } //判断当前字符是否为数字 else if (temp >= ‘0‘ && temp <= ‘9‘) { m = 0; String tempTokens = null; // 对后面的字符进行判断是否为数字 while (temp >= ‘0‘ && temp <= ‘9‘) { analyseDate[m++] = temp; tempTokens += temp; temp = uString.charAt(++index); } // 不是数字则返回种别码,结束当前方法 keyID = 11; tempTokens = tempTokens.substring(4); list.add(index + ""); list.add(keyID + ""); list.add(tempTokens + ""); return list; } m = 0; //判断当前字符是否为其他关系运算符 String token = null; switch (temp) { case ‘<‘: // String token = null; analyseDate[m++] = temp; token += temp; if (uString.charAt(++index) == ‘=‘) { analyseDate[m++] = temp; keyID = 22; token += uString.charAt(index++); } else if (uString.charAt(++index) == ‘>‘) { analyseDate[m++] = temp; keyID = 21; token += uString.charAt(index++); } else { keyID = 23; } list.add(index + ""); list.add(keyID + ""); token = token.substring(4); list.add(token); return list; case ‘>‘: analyseDate[m++] = temp; token += temp; if (uString.charAt(++index) == ‘=‘) { keyID = 24; analyseDate[m++] = temp; token += uString.charAt(index++); } else { keyID = 20; } list.add(index + ""); list.add(keyID + ""); token = token.substring(4); list.add(token); return list; case ‘:‘: analyseDate[m++] = temp; token += temp; if (uString.charAt(++index) == ‘=‘) { keyID = 18; // analyseDate[m++] = temp; analyseDate[m++] = uString.charAt(index); token += uString.charAt(index++); } else { keyID = 17; } list.add(index + ""); list.add(keyID + ""); token = token.substring(4); list.add(token); return list; case ‘*‘: keyID = 13; break; case ‘/‘: keyID = 14; break; case ‘+‘: keyID = 15; break; case ‘-‘: keyID = 16; break; case ‘=‘: keyID = 25; break; case ‘;‘: keyID = 26; break; case ‘(‘: keyID = 27; break; case ‘)‘: keyID = 28; break; case ‘#‘: keyID = 0; break; default: keyID = -1; break; } analyseDate[m++] = temp; list.add(++index + ""); list.add(keyID + ""); list.add(temp + ""); return list; } return list; } }
程序功能:可以模拟将用户输入的代码分解成词,进行词法分析,并将其字符与种别码对应输出。
种别码表:
单词符号 |
种别码 |
单词符号 |
种别码 |
begin |
1 |
: |
17 |
if |
2 |
:= |
18 |
then |
3 |
< |
20 |
while |
4 |
<= |
21 |
do |
5 |
<> |
22 |
end |
6 |
> |
23 |
l(l|d)* |
10 |
>= |
24 |
dd* |
11 |
= |
25 |
+ |
13 |
; |
26 |
- |
14 |
( |
27 |
* |
15 |
) |
28 |
/ |
16 |
# |
0 |
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