線程「main」中的異常java.lang.NullPointerException類

Question

我在寫一篇軟件，需要在另一個文件中使用一個類。當我運行程序並放入一個值時，我在線程「main」java.lang.NullPointerException類中得到錯誤Exception。 這裏是我的代碼：

package chap8lab.salesperson; 

import javax.swing.JOptionPane; 

public class Chap8LabSalesPerson { 

public static void main(String[] args) { 
    final int LIMIT = 10; 
    Salesperson[] peep = new Salesperson[LIMIT]; 
    int i = 0, a = 0; 
    String q = "q", strInput = ""; 


    JOptionPane.showMessageDialog(null, 
     "This program collects salesperson data."); 
     while (!strInput.equals(q)) 
     { 
     strInput = JOptionPane.showInputDialog(null, 
       "Enter sales person ID (\"q\" to quit)"); 
     if (!strInput.equals(q) && !strInput.matches("[a-z][A-Z]")) 
     peep[i].setEmpID(Integer.parseInt(strInput)); 
     if (!strInput.equals(q)) 
     strInput = JOptionPane.showInputDialog(null, 
       "Enter sales amount (\"q\" to quit)"); 
     if (!strInput.equals(q) && !strInput.matches("[a-z][A-Z]")) 
     peep[i].setSalesAmt(Double.parseDouble(strInput)); 
     i++; 
     if (strInput.equals(q)) 
      i--; 
     } 
     while (a < i) 
     { 
      JOptionPane.showMessageDialog(null, 
        "Employee ID: " + peep[a].getEmpID() 
        + " Sales Ammount: " + peep[a].getSalesAmt() + "\n"); 

     a++; 
     } 
     JOptionPane.showMessageDialog(null, 
        "Thank you for using this program.\nHave a nice day!"); 
    } 

} 

這裏是我的類文件Salesperson.java：

package chap8lab.salesperson; 

public class Salesperson { 
private int empID; 
private double salesAmt; 

public Salesperson() 
{ 
    empID = 9999; 
    salesAmt = 0; 
} 

public void setEmpID(int newEmpID) 
{ 
    empID = newEmpID; 
} 

public int getEmpID() 
{ 
    return empID; 
}  
public void setSalesAmt(double newSalesAmt) 
{ 
    salesAmt = newSalesAmt; 
} 

public double getSalesAmt() 
{ 
    return salesAmt; 
} 
} 

任何幫助是極大的讚賞。

Answer 1

加入之前窺視[I]窺視[i] =新的銷售員（）.setEmpID