Brainfuck in java

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;

public class Main {
  public static void main(final String[] args) throws IOException {
    if (args.length < 1) {
      System.out.println("Expected file name to interpret");
      return;
    }

    var prog = Files.readString(Path.of(args[0]), StandardCharsets.US_ASCII);

    var dataStack = new byte[30000];
    int dataPointer = 0;

    var instrStack = new ArrayList<Integer>();
    int instrPointer = 0;

    while (instrPointer < prog.length()) {
      switch (prog.charAt(instrPointer)) {
        case '>':
          dataPointer++;
          break;
        case '<':
          dataPointer--;
          break;
        case '+':
          dataStack[dataPointer]++;
          break;
        case '-':
          dataStack[dataPointer]--;
          break;
        case '.':
          System.out.format("%c", dataStack[dataPointer]);
          break;
        case ',':
          dataStack[dataPointer] = (byte) System.in.read();
          break;
        case '[':
          var stack = 1;
          var end = instrPointer + 1;
          loop:
          while (true) {
            switch (prog.charAt(end)) {
              case '[':
                stack++;
                break;
              case ']':
                stack--;

                if (stack == 0) {
                  break loop;
                }

                break;
            }

            end++;
          }

          if (dataStack[dataPointer] == 0) {
            instrPointer = end;
          } else {
            instrStack.add(instrPointer);
          }
          break;
        case ']':
          int newPointer = instrStack.get(instrStack.size() - 1) - 1;
          instrStack.remove(instrStack.size() - 1);
          if (dataStack[dataPointer] != 0) {
            instrPointer = newPointer;
          }
          break;
      }

      instrPointer++;
    }
  }
}