我不能这样做吗？收到“例外”错误 [英] Can I not do this? Getting an 'exception' error

问题描述

得到以下错误： .Exception in thread main java.lang.NullPointerException

Getting the following error: ".Exception in thread "main" java.lang.NullPointerException "

    // Creates 10 accounts
         Account[] AccArray = new Account[10];
// Data fields
        double atmVal;

// Sets each account's discrete id and initial balance to 100
         for (int i=0;i<10;i++){
            AccArray[i].setId(i); // this line is specified in the error
            AccArray[i].setBalance(100);
         }

这个编译的很好，但是我得到了例外（不确定那些是）。

This compiled fine, but I get an "exception" (not sure what those are, yet).

我根本看不出什么问题，至少在这里看不到。在这种情况下，我将添加更多代码。

I don't see what's wrong at all, at least not here. If that's deemed to be the case, I'll add more of my code.

推荐答案

您的数组已经初始化为包含10个帐户，但它们仍然为空。将循环更改为：

Your array is already intialized to contain 10 accounts, but they are all still null. Change your loop to be:

 for (int i=0;i<10;i++){
        ArrArray[i] = new Account(); // whatever constructor parameters are needed
        AccArray[i].setId(i); // this line is specified in the error
        AccArray[i].setBalance(100);
     }

话虽如此，我建议您使用小写字母命名变量（例如 accArray ）。

That being said I recommend you name your variables with lowercase names (e.g. accArray).

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