nul

To fix the bug, disallow null as a valid topping ( really the fault of index. php, but you can idiot-proof the add() function) and remove duplicates in the toppings.

为了纠正这个bug，不允许null作为有效的配料（这实际上是index.php的错误，但是可以在add（）函数中增加保护措施）并删除重复的配料。

Failure. The NULL value has been passed as a parameter.

失败. 将空指针NULL传给了一个参数.

Forecaster Dr Aidan Nulty said yesterday's storm was unusual for the time of year.

气象预报员AidanNulty博士说昨天的暴风雨在今年这个时候发生是不正常的.

Dead mappings could be eliminated by periodically scanning the Map, calling get() on each weak reference, and removing the mapping if get() returns null.

可以通过周期性地扫描Map，对每一个弱引用调用get（），并在get（）返回null时删除那个映射而消除死映射。

If mem block is NULL, pointer is ignored and free immediately returns.

如果NULL内存块,操作将被忽略并且函数立即返回.

Because the WordNet documents don't contain any relative URIs, this parameter can be given as null.

因为WordNet文档不包含任何相对URI，所以此参数可以指定为null。

Strings are initialized to null, not empty string.

String是被初始化为null, 不是空字符.

This function returns the replaced node on success, or NULL on failure.

如果函数执行成功,将返回替换的节点;如果执行失败, 将返回null[空值].

If the weak reference has been cleared ( either because the referent has already been garbage collected or because someone called WeakReference. clear()), get() returns null.

如果弱引用被清除了（不管是referent已经被垃圾收集了，还是有人调用了WeakReference.clear（）），get（）会返回null。