我使用Java使用Eclipse，出現此錯誤："Variable name" cannot be resolved to a variable.使用此Java程序：public class SalCal {    private int hoursWorked;    public SalCal(String name, int hours, double hoursRate) {        nameEmployee = name;        hoursWorked = hours;        ratePrHour = hoursRate;    }    public void setHoursWorked() {        hoursWorked = hours;     //ERROR HERE, hours cannot be resolved to a type    }    public double calculateSalary() {        if (hoursWorked <= 40) {            totalSalary = ratePrHour * (double) hoursWorked;        }        if (hoursWorked > 40) {            salaryAfter40 = hoursWorked - 40;            totalSalary = (ratePrHour * 40)                + (ratePrHour * 1.5 * salaryAfter40);        }        return totalSalary;    }}是什么導致此錯誤消息？