An Android Input filter that validates the range of an input. The ones on stackoverflow does not seem to understand the meaning of the parameters of the filter method

RangedInputFilter.java

    class RangedInputFilter implements InputFilter {

        private int fieldSize;

        private int min, max;

        RangedInputFilter(int fieldSize, int min, int max) {
            this.fieldSize = fieldSize;
            if (min > max) {
                throw new IllegalArgumentException("Min value should be less or equal to max");
            } else {
                this.min = min;
                this.max = max;
            }
        }

        @Override
        public CharSequence filter(CharSequence source, int start, int end, Spanned dest,
                int dstart, int dend) {

            // Compute new string after edition
            StringBuilder builder = new StringBuilder(dest);
            if (dstart > (dest.length() - 1)) {
                builder.append(source);
            } else {
                builder.replace(dstart, dend, source.toString().substring(start, end));
            }

            String newString = builder.toString();

            // Only valid when input is will be complete as intermediate input
            // may be temporally invalid
            if (newString.length() == fieldSize) {
                try {
                    int newValue = Integer.parseInt(newString);
                    if ((min <= newValue) && (newValue <= max)) {
                        return null; // Accept
                    } else {
                        return ""; // Reject
                    }
                } catch (NumberFormatException e) {
                    return ""; // Reject input
                }
            } else {
                return null; // Accept input
            }

        }

    }