Extract strings outside square brackets

Question

If I have a BNF code like this

[A] ::= [A]B | C | [D]
[D] ::= C[D] | C

how can I extract letters that are not inside square brackets. I have tried this

for(int i=0;i<lineNumber;i++)
    {
       String Data[]=data[i].split("::=");
       Nonter.add(Data[0]);
       ter.add(Data[1]);
       NterSay++;

    }

   String[] splitted = ter.get(0).split("\\[|\\]|\\|");
   for (String split: splitted) {      
System.out.println(split);

}

But it prints all the letters.

Answer 1

Try this:

    String[] data = new String[]{"[A] ::= [A]B | C | [D]", "[D] ::= C[D] | C"};
    List<String> nonter = new ArrayList<>();
    List<String> ter = new ArrayList<>();

    for (String aData : data) {
        String Data[] = aData.split("::=");
        nonter.add(Data[0]);
        ter.add(Data[1]);
    }

    String replaced = ter.get(0).replaceAll("\\[\\w]|\\s|\\|", "");

    for (char ch : replaced.toCharArray()) {
        System.out.println(ch);
    }