This means that an object is initialized with a value and not reassigned.
这意味着用一个值初始化对象，以后不再重新赋值。
Because it is not, thread 2 returns the instance reference to a fully constructed, but partially initialized, Singleton object.
因为实例不为null，线程2将instance引用返回给一个构造完整但部分初始化了的Singleton对象。
The Discussions object has already been initialized, and can not be reinitialized.
讨论对象已经初始化，并且不能重新初始化。
It is not possible for an object or collection initializer to refer to the object instance being initialized.
对于某个对象或集合的构造者而言，引用该对象实例进行初始化是不可能的。
The assignment operator is applied on a initialized object, but this is not the case in the copy constructor.
赋值运算符是应用于一个初始化的对象，但这并不是拷贝构造函数的情况下。
Both of your cases checks if the object is equal to nil (is not initialized) and both will work.
你的两例检查对象是否等于零(未初始化)，将工作。
Because the new instance of the object is initialized to zero and no constructors are run, the object might not represent a state that is regarded as valid by that object.
因为物件的新执行个体会初始化为零，并且建构函式不会执行，所以物件可能不会表示由该物件视为有效的状态。
Because the new instance of the object is initialized to zero and no constructors are run, the object might not represent a state that is regarded as valid by that object.
因为物件的新执行个体会初始化为零，并且建构函式不会执行，所以物件可能不会表示由该物件视为有效的状态。
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