无法添加元素ArrayList的for循环 [英] Can't add element to ArrayList in for loop

问题描述

我目前具有不能够运行在Android应用开发以下code中的问题。

I am currently having the problem of not able to run the following code in Android app development.

import java.util.ArrayList;

public class Test extends FragmentActivity {

ArrayList<String> random;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
        for (int a=0; a<11; a++){
        random.add("a");
    }
            }
    }

我知道上面code做无用的动作，但是是从我的问题，简化了Java中环code。而我从错误日志，未处理的事件循环异常这个错误。任何人都可以指出的是什么，我做错了吗？

I know the above code does useless action but that is simplified from my problem in the for loop code in JAVA. And I got this error from the error log, "unhandled event loop exception". Can anyone point out that what I am doing wrong please?

推荐答案

有至少两个问题（我怀疑）。

There are at least two problems (I suspect).

首先，你得到 NullPointerException异常因为你没有初始化随机用值指的是一个实际的对象。

First, you're getting a NullPointerException because you're not initializing random with a value referring to an actual object.

接下来，你的语法是坏在这里：

Next, your syntax is bad here:

for (int a=0; a<11; a++);

您code仅增加单个元素随机 - 这是等同于：

Your code is only adding a single element to random - it's equivalent to:

for (int a=0; a<11; a++)
{
}
random.add("a");

我很怀疑这是你打算什么。我的猜测是，你想这个代替：

I very much doubt that that's what you were intending. My guess is that you wanted this instead:

for (int a=0; a<11; a++)
{
    random.add("a");
}

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