增强了对象的循环和空检查 [英] Enhanced for loop and null check of objects

问题描述

让我说我有以下代码:

for (AnyObject anyObject : anyObjectList) {
    System.out.println(anyObject.doSomething());
}

我的问题是:我读到它有可能在至少某种列表类型中添加null. 如果我说对了:在访问迭代类的方法之前，不总是应该有一个null检查吗? 我只是问，因为到目前为止我从未见过像这样的空检查增强的for循环:

My question is: I read that its possible to add null to at least some kind of list types. If im right: shouldn't be there always a null check before you access the method of the iterated class? Im just asking because i have never seen so far a enhanced for loop with a null check like this for example:

for (AnyObject anyObject : anyObjectList) {
    if (anyObject != null) {
        System.out.println(anyObject.doSomething());
    }
}

推荐答案

实际上，您经常想知道列表中是否有随机的null，而不应该出现.您的第一个代码段将引发异常以指示问题，而第二个代码段将静默使用该错误.

Actually you'd often want to know if there is a random null in your list when there shouldn't be. Your first snippet will throw an exception indicating the problem, but your second will consume the error silently.

您还可以执行以下操作:

You could also do something like this:

for (AnyObject anyObject : anyObjectList) {
    if (anyObject != null) {
        System.out.println(anyObject.doSomething());
    } else {
        /* something went wrong -- report error, debugging info, etc. */
    }
}

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