Java org.objectweb.asm findPattern

// maybe I have been bad and haven't completely tested everything

public class AsmHelper {
    public static void main(String[] args) {}

    public static void printPatternAndMask(AbstractInsnNode start) {
        StringBuilder pattern = new StringBuilder(), mask = new StringBuilder();
        AbstractInsnNode next = start;
        do {
            pattern.append("0x");
            if(next.getOpcode() != F_NEW) {
                mask.append("x");
                pattern.append(Integer.toHexString(next.getOpcode()));
            } else {
                mask.append("?");
                pattern.append("00");
            }
            pattern.append("\\");
            next = next.getNext();
        } while(next != null);

        System.out.printf("\nPattern: " + pattern.toString() + "\n");
        System.out.printf("\nMask: " + mask.toString() + "\n");
    }

    public static int[] convertPattern(String pattern) {
        if(pattern.startsWith("\0"))
            pattern = pattern.substring(1);
        String[] hex = pattern.split("\0");
        int[] buff = new int[hex.length];
        int index = 0;
        for(String number : hex) {
            if(number.startsWith("0x"))
                number = number.substring(2);
            else if(number.startsWith("x"))
                number = number.substring(1);
            buff[index++] = Integer.parseInt(number, 16);
        }
        return buff;
    }

    public static AbstractInsnNode findPattern(AbstractInsnNode start, String pattern, String mask) {
        return findPattern(start,
                convertPattern(pattern),
                mask.toCharArray());
    }

    public static AbstractInsnNode findPattern(AbstractInsnNode start, int[] pattern, char[] mask) {
        if(start != null &&
                pattern.length == mask.length) {
            int found = 0;
            AbstractInsnNode next = start;
            do {
                switch(mask[found]) {
                    // Analyze this node
                    case 'x': {
                        // Check if node and pattern have same opcode
                        if(next.getOpcode() == pattern[found]) {
                            // Increment number of matched opcodes
                            found++;
                        } else {
                            // Go back to the next node of the first matching node
                            for(int i = 1; i <= (found - 1); i++)
                                next = next.getPrevious();
                            // Reset the number of opcodes found
                            found = 0;
                        }
                        break;
                    }
                    // Skips over this node
                    default:
                    case '?':
                        found++;
                        break;
                }
                // Check if found entire pattern
                if(found >= mask.length) {
                    // Go back to top node
                    for(int i = 1; i <= (found - 1); i++)
                        next = next.getPrevious();
                    return next;
                }
                next = next.getNext();
            } while(next != null &&
                    found < mask.length);
        }
        return null;
    }
}