BrainF interpreter in Java

BFJ.java

package net.benjaminurquhart.bfj;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;

import javax.script.ScriptException;

public class BFJ {

	public static String stripComments(String code){
		return code.chars().mapToObj((c) -> ((char)c)+"").filter((c)->",.+-<>[]".contains(c)).reduce("",(x,y)->x+y);
	}
	public static void execute(String code) throws ScriptException{
		execute(code, 30000);
	}
	public static void execute(String code, int cellAmount) throws ScriptException{
		int[] buff = new int[cellAmount < 30000 ? 30000 : cellAmount];
		ArrayList<BracketPair> bracketsQueue = new ArrayList<>(), brackets = new ArrayList<>();
		int instruction = 0, data = 0, codeLen = code.length();
		for(int i = 0; i < codeLen; i++){
			try{
				if(code.charAt(i) == '[') bracketsQueue.add(0, new BracketPair(i, 0));
				if(code.charAt(i) == ']') brackets.add(bracketsQueue.remove(0).setB(i));
			}
			catch(IndexOutOfBoundsException e){
				throw new ScriptException("Unmatched jump instruction at character " + i);
			}
		}
		if(!bracketsQueue.isEmpty()){
			throw new ScriptException("Unmatched jump instruction at character " + bracketsQueue.get(0).getF());
		}
		HashMap<Integer, Integer> forward = new HashMap<>(), backward = new HashMap<>();
		for(BracketPair pair : brackets){
			if(pair.getB() == pair.getF()){
				throw new ScriptException("Invalid jump instruction at character " + pair.getB());
			}
			backward.put(pair.getF(), pair.getB());
			forward.put(pair.getB(), pair.getF());
		}
		try{
			while(instruction < codeLen){
				switch(code.charAt(instruction)){
				case ',': buff[data] = System.in.read(); break;
				case '.': System.out.print((char)buff[data]); break;
				case '+': buff[data]++; break;
				case '-': buff[data]--; break;
				case '>' : data++; break;
				case '<' : data--; break;
				case '[': instruction = (buff[data] == 0 ? backward.get(instruction) : instruction); break;
				case ']': instruction = (buff[data] != 0 ? forward.get(instruction) : instruction); break;
				}
				if(data >= buff.length || data < 0){
					throw new ScriptException(String.format("Out-of-bounds buffer access at character %d. Index: %d, Size: %d", instruction, data, buff.length));
				}
				instruction++;
			}
		}
		catch(IOException e){
			throw new ScriptException("Failed to read from standard input: " + e.getMessage());
		}
	}
}
class BracketPair{
	
	private int f,b;
	
	protected BracketPair(int f, int b){
		this.f = f;
		this.b = b;
	}
	protected BracketPair setF(int f){
		this.f = f;
		return this;
	}
	protected BracketPair setB(int b){
		this.b = b; 
		return this;
	}
	protected int getF(){
		return f;
	}
	protected int getB(){
		return b;
	}
}