Page History

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• Returning this from a nonprivate (possibly final) method invoked from the constructor of an object under construction
• Passing this as an argument to an alien method invoked from the constructor of an object under construction
• Publishing this using public static variables from the constructor of an object under construction
• Publishing this such that pieces of code beyond its current scope can obtain its reference
• Calling a non-final method from a constructor (MET04-J. Ensure that constructors do not call overridable methods)
• Overriding the finalizer of a non-final class and obtaining the this reference of a partially constructed initialized instance, when the construction of the object ceases (OBJ04-J. Do not allow partially initialized objects to be accessed)
• Passing internal object state to an alien method and consequently, exposing the this reference of internal objects

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This ensures that threads do not see a compromised Publisher instance. The num variable is also declared as final; consequently, the class is immutable. There is no threat of a caller invoking newInstance() to obtain a partially constructed initialized object because pu is not returned until the construction of the object is over.

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Because the constructor is private, untrusted code cannot create instances of the class, prohibiting the this reference from escaping. Using a public static factory method to create new instances also protects against publication of partially constructed initialized objects (CON26-J. Do not publish partially initialized objects).

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