Abstract
YYou will find this design pattern useful when you need to guarantee that there is only a single instance of a class available during execution.
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Notes
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Though not a need, many users now prefer a multiple-monitor configuration.
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GoF , p. 127.
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In ABAP, a class marked as create private will confer create none upon any subclasses, preventing them from both being instantiated and creating instances of the superclass. Accordingly, SAP recommends including the final qualifier in the definition of those classes that are assigned create private instantiability.
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Such references, where any one of the three components could use up to the full 30-character maximum length of its respective component name, would not have been possible years ago in releases of SAP environments such as R/3 where the ABAP editor restricted the width of a single line to 72 characters. Extending this editor line width restriction, which now stands at 255 characters, made it possible to construct such long compound references without having to resort to cumbersome techniques to avoid overrunning the line end barrier.
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© 2017 James E. McDonough
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McDonough, J.E. (2017). Singleton Design Pattern. In: Object-Oriented Design with ABAP. Apress, Berkeley, CA. https://doi.org/10.1007/978-1-4842-2838-8_11
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DOI: https://doi.org/10.1007/978-1-4842-2838-8_11
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