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Constructor Rules

 
Greenhorn
Posts: 21
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Hi,

Can anybody explain this point with a sample program.

Constructors can use any access modifier, including private.(A private constructor means only code within the class itself can instantiate an object of that type, so if the private constructor class wants to allow an instance of the class to be used, the class must provide a static method or variable that allows access to an instance created from within the class).
 
Sheriff
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For an example, look at java.text.DateFormat. Here, the contructor is protected, not private, but that will still disallow public construction of a DateFormat object. If you want one, you have to call one of the DateFormat.get*Instance() methods instead.
 
Ranch Hand
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Consider the Singleton pattern:

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