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What is a NullPointerException, and how do I fix it?（12个答案）
11个月前关闭。
我的问题通常很简单，但我就是不明白问题出在哪里。-我正在声明一个类的数组作为全局变量，我在另一个类中的多个函数中重用它。示例化的类是：

public class Service {
      int numticketsin;
            String name="mi";
            int[] perhour={0,0,0,0,0,0,0,0,0,0};

            int moyenneticketperday;
            int[] moyenneticketperdayperhour={0,0,0,0,0,0,0,0,0,0};
            public Service(){}
}

全局变量：

Service[] services=new Service[10];

下面的函数是用来填充数组的：

public void getnamesofservices(){
        int x=0;
        Connection conn=db.java_db();

        try {   
             Statement stmt = conn.createStatement();

                String qry = "SELECT  service_name from service ";

                ResultSet rs = stmt.executeQuery(qry);
                int i=0;
                while (rs.next()) {
                        String namee=rs.getString("service_name");
                        System.out.println(namee);

                        services[i].name = namee;
                   i++;
                }
                conn.close();

        }
        catch (SQLException ex)
            {
            System.err.println("SQLException: " + ex);
        }

    }

错误：

''' Exception in thread "main" java.lang.NullPointerException: Cannot assign field "name" because "this.services[i]" is null
    at com.mycompany.stats.NewJFrame.getnamesofservices(NewJFrame.java:195)
    at com.mycompany.stats.NewJFrame.<init>(NewJFrame.java:122)
    at com.mycompany.stats.Main.main(Main.java:16)'''

提前谢谢你！！