我不断获得nullPointerException
,其余代码将无法运行。我有两个班级设置。一个是SalesPerson
,另一个是main
方法。标记了第42行,这是nullPointerException
出现的位置。
这是第42行
System.out.printf("%-20s %15.2f %14.2f %n", list[i].getFirstName() + " " + list[i].getLastName(), list[i].getTotalSales(), list[i].getSalary());
public class SalesPerson {
private String firstName;
private String lastName;
private double firstSales;
private double secondSales;
private double thirdSales;
private double fourthSales;
private double totalSales;
private double salary;
public SalesPerson(String lastName, String firstName, double firstSales,
double secondSales, double thirdSales, double fourthSales,
double totalSales, double salary) {
this.lastName = lastName;
this.firstName = firstName;
this.firstSales = firstSales;
this.secondSales = secondSales;
this.thirdSales = thirdSales;
this.fourthSales = fourthSales;
this.totalSales = totalSales;
this.salary = salary;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public double getTotalSales() {
return totalSales;
}
public void setTotalSales(double totalSales) {
this.totalSales = totalSales;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public double getFirstSales() {
return firstSales;
}
public void setFirstSales(double firstSales) {
if (firstSales >= 0) {
this.firstSales = firstSales;
} else {
System.out.println("First sales must be greater than zero.");
}
}
public double getSecondSales() {
return secondSales;
}
public void setSecondSales(double secondSales) {
if (secondSales >= 0) {
this.secondSales = secondSales;
} else {
System.out.println("Second sales must be greater than zero.");
}
}
public double getThirdSales() {
return thirdSales;
}
public void setThirdSales(double thirdSales) {
if (thirdSales >= 0) {
this.thirdSales = thirdSales;
} else {
System.out.println("Third sales must be greater than zero.");
}
}
public double getFourthSales() {
return fourthSales;
}
public void setFourthSales(double fourthSales) {
if (fourthSales >= 0) {
this.fourthSales = fourthSales;
} else {
System.out.println("Fourth sales must be greater than zero.");
}
}
}
第二课
import java.io.File;
import java.util.Scanner;
public class Assignment10 {
public static final int NUM_SALESPEOPLE = 20;
public static final double NUM_PER_SALARY = 25;
public static void main(String[] args) {
SalesPerson[] list = new SalesPerson[NUM_SALESPEOPLE];
try {
int people = 0;
Scanner fileInput = new Scanner(new File("A10.txt"));
while (fileInput.hasNext()) {
String lastName = fileInput.next();
String firstName = fileInput.next();
double firstSales = fileInput.nextDouble();
double secondSales = fileInput.nextDouble();
double thirdSales = fileInput.nextDouble();
double fourthSales = fileInput.nextDouble();
double totalSales = firstSales + secondSales + thirdSales + fourthSales;
double salary = NUM_PER_SALARY * totalSales;
SalesPerson person = new SalesPerson(lastName, firstName,
firstSales, secondSales, thirdSales, fourthSales, totalSales, salary);
list[people] = person;
people++;
}
} catch (Exception ex) {
System.out.println("Error opening file.");
}
System.out.println("Full Name Total Sales Salary");
System.out.println("========= =========== ======");
for (int i = 0; i < NUM_SALESPEOPLE; i++) {
System.out.printf("%-20s %15.2f %14.2f %n", list[i].getFirstName() + " " + list[i].getLastName(), list[i].getTotalSales(), list[i].getSalary());
}
System.out.println("===================================================");
}
}
答案 0 :(得分:5)
您正在创建一个大小为20的数组。此数组仅包含对NULL的引用。如果您的文件中包含的条目少于20个,则最终会产生nullpointerexception。
可以肯定的是,尝试打印人的价值。如果小于20则这是正常的。
答案 1 :(得分:1)
您的文件'A10.txt'没有20行(正确)。
您不应该创建数组。请改用ArrayList
和Iterator
来解决问题。
答案 2 :(得分:0)
只需添加一个null检查:
for (int i = 0; i < NUM_SALESPEOPLE; i++) {
if (list[i] != null) {
System.out.printf("%-20s %15.2f %14.2f %n", list[i].getFirstName() + " " + list[i].getLastName(), list[i].getTotalSales(), list[i].getSalary());
}
}
或声明
int people = 0;
之前的两行(在try-block之前)并使用此数量的实际读取人数作为for循环的上限,而不是NUM_SALESPEOPLE
。