FullBuisnessOperation_1.java

public abstract Result<Integer> readIntFromFile(String file);

public Result<Integer> adjustValue(Integer value) {
    if (value > 5) {
        Result.error("Value " + value + " should no be greater than 5");
    }

    return Result.ok(5 - value);
}

public Double calculateAverage(Integer val1, Integer val2) {
    return (val1 + val2)/2d;
}

/**
 * Read ints from two files, Adjust the first one and then calculate average.
 * Returns a Result wrapping the positive outcome or any error.
 */
public Result<Double> businessOperation(String fileName, String fileName2) {
    Result<Integer> val1 = readIntFromFile(fileName);

    if (val1.isError()) {
        return Result.error(val1.getError());
    }

    Result<Integer> adjusted1 = adjustValue(val1.getValue());

    if (adjusted1.isError()) {
        return Result.error(adjusted1.getError());
    }

    Result<Integer> val2 = readIntFromFile(fileName2);

    if (val2.isError()) {
        return Result.error(val2.getError());
    }

    Double average = calculateAverage(adjusted1.getValue(), val2.getValue());
    return Result.ok(average);
}