Editing Object copying (section)

=== Shallow copy ===
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One method of copying an object is the ''shallow copy''. In that case a new object B is [[object creation|created]], and the fields values of A are copied over to B.<ref>{{cite web|title=C++ Shallow vs Deep Copy Explanation|url=http://www.fredosaurus.com/notes-cpp/oop-condestructors/shallowdeepcopy.html}}</ref><ref>{{cite web|title=.NET Shallow vs Deep Copy Explanation|url=http://www.codeproject.com/Articles/28952/Shallow-Copy-vs-Deep-Copy-in-NET}}</ref><ref>{{cite web|title=Generic Shallow vs Deep Copy Explanation|url=https://secweb.cs.odu.edu/~zeil/cs361/web/website/Lectures/big3/pages/shallowvsdeep.html|access-date=2013-04-10|archive-url=https://web.archive.org/web/20160304115828/https://secweb.cs.odu.edu/~zeil/cs361/web/website/Lectures/big3/pages/shallowvsdeep.html|archive-date=2016-03-04|url-status=dead}}</ref> This is also known as a ''field-by-field copy'',<ref>Core Java: Fundamentals, Volume 1, [https://books.google.com/books?id=QTZvAQAAQBAJ&pg=PA295&dq=%22field+copy%22 p. 295]</ref><ref>''[[Effective Java]]'', Second Edition, [https://books.google.com/books?id=ka2VUBqHiWkC&pg=PA54&dq=%22field+copy%22 p. 54]</ref><ref>"[https://stackoverflow.com/questions/2890340/what-is-this-field-by-field-copy-done-by-object-clone What is this field-by-field copy done by Object.clone()?]", ''Stack Overflow''</ref> ''field-for-field copy'', or ''field copy''.<ref>"Josh Bloch on Design: A Conversation with Effective Java Author, Josh Bloch", by Bill Venners, ''JavaWorld'', January 4, 2002, [http://www.artima.com/intv/bloch13.html p. 13]</ref> If the field value is a reference to an object (e.g., a memory address) it copies the reference, hence referring to the same object as A does, and if the field value is a primitive type, it copies the value of the primitive type. In languages without primitive types (where everything is an object), all fields of the copy B are references to the same objects as the fields of original A. The referenced objects are thus ''shared'', so if one of these objects is modified (from A or B), the change is visible in the other. Shallow copies are simple and typically cheap, as they can usually be implemented by simply copying the bits exactly.