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Thread: Method to count objects

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    Default Method to count objects

    Is it possible to write a method that will count the number of object created?

    In the past, I have counted objects by declaring a integer count variable and incrementing each time that constructor is called. However, I now want to write a method that will count objects on its own. For instance:

    public class MyClass
    {
         private int numMyClass;
     
         public int countMyClassObjs
         {
              //Code that counts instances of MyClass
              return numMyClass;
         }
    }


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    Super Moderator helloworld922's Avatar
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    Default Re: Method to count objects

    In pure Java, no. Java has no way to peer into the memory without proper references. There is also a problem with counting the number of objects there are in this manner:

    When an object gets destructed, there is no mechanism implemented to decrease the count.

    The easy solution is to override the finalize method and decrease that counter whenever the object actually gets destructed (note: even though an object goes out of scope or has no more references to it, it does not get destructed right away)

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    Super Moderator Json's Avatar
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    Default Re: Method to count objects

    If this is just for profiling purposes, try out JVisualVM, comes with the JDK nowadays

    // Json

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    Default Re: Method to count objects

    Quote Originally Posted by Json View Post
    If this is just for profiling purposes, try out JVisualVM, comes with the JDK nowadays

    // Json
    I'm not sure I understand what you mean. Could you elaborate?

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    Default Re: Method to count objects

    Well for one, make the method static otherwise the feild "numMyClass" is a new value every instance, and in terms of removing, you need to override the "finalize" method, called by the garbage collector, and use that to decrease the value.

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    Default Re: Method to count objects

    Quote Originally Posted by helloworld922 View Post
    The easy solution is to override the finalize method and decrease that counter whenever the object actually gets destructed (note: even though an object goes out of scope or has no more references to it, it does not get destructed right away)
    But there is no guarantee that an object finalizer will ever be called, so it's not really a reliable solution.

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