英文:
Cannot read the array length because "this.weeklyHours" is null
问题
我在calculateTotalPay方法和calculateAveragePay方法中遇到了java.lang.NullPointerException错误。错误消息指出它无法读取数组长度，因为this.weeklyHours是null。
public double calculateAveragePay() {double averagePay = 0;double totalPay = 0;// totalPay = calculateTotalPay();averagePay = totalPay / weeklyHours.length;return averagePay;}public double calculateTotalPay() {int totalAmount = 0;// for (int index = 0; index < weeklyHours.length; index++)totalAmount += weeklyHours[index];return totalAmount;}
public class Employee {private static final int DEFAULT_WEEKS = 52;private String name;private double salary;private double[] weeklyHours;//private int numWeeks;public Employee(String name, double salary) {this.name = name;this.salary = salary;double[] weeklyHours = new double[DEFAULT_WEEKS];}public Employee(String name, double salary, int numWeeks) {this.name = name;this.salary = salary;double[] weeklyHours = new double[numWeeks];}}
英文:
I am getting a java.lang.NullPointerException error for my calculateTotalPay method and calculateAveragePay method. The error message states that it cannot read the array length because this.weeklyHours is null.
public double calculateAveragePay() {double averagePay = 0;double totalPay = 0;// totalPay = calculateTotalPay();averagePay = totalPay / weeklyHours.length;return averagePay;}public double calculateTotalPay() {int totalAmount = 0;// for (int index = 0; index < weeklyHours.length; index++)totalAmount += weeklyHours[index];return totalAmount;}
public class Employee {private static final int DEFAULT_WEEKS = 52;private String name;private double salary;private double[] weeklyHours;//private int numWeeks;public Employee(String name, double salary) {this.name = name;this.salary = salary;double[] weeklyHours = new double[DEFAULT_WEEKS];}public Employee(String name, double salary, int numWeeks) {this.name = name;this.salary = salary;double[] weeklyHours = new double[numWeeks];}
答案1
得分: 2
你在两个构造函数中都有相同的错误。你正在用一个新的局部变量遮蔽了字段。像你对其他字段做的那样使用 this 来避免这类错误。
public Employee(String name, double salary) {this.name = name;this.salary = salary;this.weeklyHours = new double[DEFAULT_WEEKS];}public Employee(String name, double salary, int numWeeks) {this.name = name;this.salary = salary;this.weeklyHours = new double[numWeeks];}
你可以用以下方式替换第一个构造函数：
public Employee(String name, double salary) {this(name, salary, DEFAULT_WEEKS);}
英文:
You have the same bug in both constructors. You are shadowing the field with a new local variable. Use this like you did with the other fields to avoid this class of error.
public Employee(String name, double salary) {this.name = name;this.salary = salary;// double[] weeklyHours = new double[DEFAULT_WEEKS];this.weeklyHours = new double[DEFAULT_WEEKS];}public Employee(String name, double salary, int numWeeks) {this.name = name;this.salary = salary;// double[] weeklyHours = new double[numWeeks];this.weeklyHours = new double[numWeeks];}
You could replace the first constructor with
public Employee(String name, double salary) {this(name, salary, DEFAULT_WEEKS);}
答案2
得分: 0
从_Employee_类的构造方法内部，您正在初始化一个_局部变量_，而不是分配_类变量_。
double[] weeklyHours = new double[DEFAULT_WEEKS];
double[] weeklyHours = new double[numWeeks];
只需删除声明类型，即可访问_类变量_。
weeklyHours = new double[DEFAULT_WEEKS];
weeklyHours = new double[numWeeks];
英文:
From within the Employee class constructor methods, you're initializing a local variable, as opposed to assigning the class variable.
double[] weeklyHours = new double[DEFAULT_WEEKS];
double[] weeklyHours = new double[numWeeks];
Just remove the declaration type, to access the class variable.
weeklyHours = new double[DEFAULT_WEEKS];
weeklyHours = new double[numWeeks];
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