Question

我无法初始化对象数组。我一直收到错误（NullPointerException），我尝试了几种不同的初始化方法。我是java的新手（从c ++开始）。我想也许我需要为Customer类创建一个构造函数，但是当我尝试它时它不起作用。有任何想法吗？提前致谢。（这些只是我代码的片段）

更新：好的，所以我替换了声明，我仍然在几行上得到nullpointerexception错误，这里是更新的代码。我初始化Customer类的私有错了吗？再次感谢帮助人们，非常感谢。

更新2：因此，经过一些修补，我创建了一个for循环，单独初始化类对象数组的每个索引。非常感谢！

public static class ATM{
    private double funds = 100;
    private int serial;
    private String location = "UNKNOWN", bank_name;
    private int succ_with = 0, fail_with =0;
    private Customer[] customers = new Customer[10];///////updated here
    public void custSet(String u, String b, int p, double bal, Customer[] customer, int index)
    {
        customer[index].user_name = u;
        customer[index].bank_name = b;//second exception 
        customer[index].balance = bal;
        customer[index].pin = p;
    }
    public void populateCust()
    {

        custSet("Alice","OtterUnion",1234,5000.0,customers,0);//3rd exception
        custSet("Tom","OtterUnion",2000,200.0,customers,1);
        custSet("Monica","OtterUnion",3000,50.0,customers,2);
        custSet("Michael", "OtterUnion",7777,0.00,customers,3);
        custSet("John","OtterUnion",8000,500.00,customers,4);
        custSet("Jane","OtterUnion",2222,500.00,customers,5);
        custSet("Robert","BOA",2323,200.00,customers,6);
        custSet("Owen","BOA",4455,50.00,customers,7);
        custSet("Chris","BOA",8787,10.00,customers,8);
        custSet("Rebecca","BOA",8080,555.55, customers,9);
    }

    }
public static class Customer{
    private String user_name, bank_name;
    private int pin;//(first exception complaining about this, but when i 
    // change it to public the error goes away, so Ill just need to make a setter
    private double balance;
}

Answer 1

您需要在使用之前实例化您的数组：customers = new Cusomter [size]

空指针异常java数组初始化

1 个答案: