Destructor (Java and Delphi Cross Reference Guide)

General Info: Class Destructor

A special class method called when an object instance of a class is destroyed. With some languages they are called when the object instance goes out of scope, with some languages you specifically have to call the destructor in code to destroy the object, and others use a garbage collector to dispose of object instances at specific times.

Desctructors are commonly used to free the object instance but with languages that have a garbage collector object instances are disposed of when appropriate. Either way, destructors or their equivalent are commonly used to free up resources allocated in the class constructor.

Languages Focus

Are object instances freed with a garbage collector? Or, do you have to destroy object instances.

Java:  "finalize" finalize() Java has a garbage collection algorythm that runs as a background task so it has no destructors. You can use the finalize() method to close additonal resources such as file handles. Syntax Example: protected void finalize() throws Throwable { try { close(); // close open files } finally { super.finalize(); } }

Delphi:   Free or FreeAndNil Object Pascal uses a standard virtual destructor named Destroy which is called by the standard Free method. All objects are dynamic, so you need to call MyObject.Free method or the FreeAndNil(MyObject) routine for each object you create. Syntax Example:   var MyObject: TObject; begin MyObject := TObject.Create; //Use it... MyObject.Free //Or use...FreeAndNil(MyObject); end;