我正在使用java来实现一个通用代码来解决语法中的左递归问题，所以我的代码工作如下我正在读取这样的输入，因为每行都转到下一行：
E
E+T|T
T
T*F|F
F
(E)|id|number
并且所需的输出应该像这样：
E->[TE']
T->[FT']
F->[(E), id, number]
E'->[+TE', !]
T'->[*FT', !]
我编写了代码，它将输入存储在Arraylists中以迭代它们并产生输出：
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
public class IleftRecursion {
//storing each line in its corresponding Arraylist
static ArrayList<String> leftRules = new ArrayList<>();
static ArrayList<String> rightRules = new ArrayList<>();
public static void read_file(String file) throws IOException {
FileReader in = new FileReader(file);
BufferedReader br = new BufferedReader(in);
String line;
while ((line = br.readLine()) != null) {
leftRules.add(line);
rightRules.add(br.readLine());
}
br.close();
}
public static void ss() {
for (int i = 0; i < leftRules.size(); i++) {
for (int j = 1; j <= i - 1; j++) {
//splitting inputs on bars "|" to iterate through them
for (String x : rightRules.get(i).split("\\|")) {
if (x.contains(leftRules.get(j))) {
String f = "";
String ff = "";
for (int k=0; k<rightRules.get(k).split("\\|").length;k++) {
f = x;
f = f.replaceAll(leftRules.get(i), rightRules.get(k).split("\\|")[k]);
ff += f;
}
rightRules.remove(i);
rightRules.add(i, ff);
}
}
}
//Recursive or Not boolean
boolean isRec = false;
for (String z : rightRules.get(i).split("\\|")) {
if (z.startsWith(leftRules.get(i))) {
isRec = true;
break;
}
}
if (isRec) {
String a = "";
String b = "";
for (String s : rightRules.get(i).split("\\|")) {
if (s.startsWith(leftRules.get(i))) {
b += s.replaceAll(leftRules.get(i), "") + leftRules.get(i) + "',";
} else {
a += s + leftRules.get(i) + "'";
}
}
b += "!";
if(a.length()>=1)
a.substring(1, a.length() - 1);
rightRules.add(i, a);
rightRules.add(i + 1, b);
leftRules.add(leftRules.get(i) + "'");
}
}
}
public static void main(String[] args) throws IOException {
read_file("Sample.in");
ss();
for (int i=0;i<leftRules.size();i++)
{
System.out.print(leftRules.get(i)+"->");
System.out.println("["+rightRules.get(i)+"]");
}
}
}
我多次调试代码试图找出为什么我得到这样的输出
E->[TE']
T->[+TE',!]
F->[T]
E'->[T*F]
缺少一条规则，而且并非所有以正确的方式生成的新作品，但我无法修复，任何人都可以帮助我完成这项工作吗？