refactoring : Java Glossary

1. I have a method which has some code that I would like to pull out into its own method.
2. I highlight the offending code.
3. I select Extract Method from a popup menu
4. The Refactoring Browser asks me to name the method and automatically creates it and inserts the highlighted code.
5. In the current method, the highlighted code is replace by an invocation to the newly created method.

Ideally, in a perfectly written computer program, with a perfectly designed computer language, with a perfect SCID/ IDE, it should be possible to change any line/element of the program in isolation without having to make any supporting changes elsewhere. The program should still function in a reasonable way. For example, you should be able to change the allowable bounds on a field variable in one line of code (which might result in it internally being promoted from int to long), without having to manually adjust any other code. The basic principle is you should have to tell a computer any one fact, or decision in only one place. For example, you should have to tell a program which colour scheme to use in precisely one and only one place and by one place I mean one line of code. Real life computer languages and IDEs (Integrated Development Environments) put up huge roadblocks to getting anywhere close to perfection.

Java is a very refactoring-friendly language. You can change the type of a variable, add or remove a parameter to a method, Change something from static to instance or the reverse. Move code around. Split code up. Rename. You can do these things with a refactoring tool such as the one in IntelliJ, but even if it or you screw up or fail to complete the changes, as soon as you compile, the error mesages will warn you of other things you must change to be consistent. Pretty much, when you get a clean compile, your code will work.

IntelliJ

• Extract Method: I highlight a block of code that might be many line or just an expression. It then turns it into a method, figures out what the parameters need to be and what type it returns. It then replaces the code with a call to the new method. It then finds similar code snippets and, with permission, also converts them to calls the new method.
• Introduce constant: converts literals to named constants. You have to give it some help to decide which instances to convert.
• Change signature: add, remove, rename, reorder the parameters of a method and automatically modify all invocations to the new rules.
• Global rename: my most common refactoring. Some people would not consider it a refactoring, but I consider it the most important tidying activity partly because it drives the decision of what code belongs where. IntelliJ renames with knowledge of Java syntax, so you don’t accidentally rename unrelated local variables with the same name. Lets you review which comments to rename. Lets you also rename similarly named variables and method in the same pop.
• Pull up: move a method or field from subclass to its superclass and make necessary adjustments. It will let you control just how much of its attached baggage of fields and methods you move with it.
• Push down: move a method or field from a superclass to one of its subclasses.
• Generify: add generics to a class.

Algebra

If you recall your grade 7 algebra, you learned to refactor. You learned to convert 7a + 7b to 7(a + b). You look for commonality then split it out so that it appears only once. This is the same thing you do to refactor Java. You look for common code. Then you split it out so there is no repetition of it. You can have two classes implement a common interface, or one class inherit from another or two classes inherit from a common base class, possibly abstract. You write the common code in using only the fields and methods of the common interface or class.

When in doubt, refactor.
~ Roedy (1948-02-04 age:70)

Books

Book referral for Refactoring Workbook

	recommend book⇒Refactoring Workbook
	by	William C. Wake	978-0-321-10929-3	paperback
	publisher	Addison-Wesley
	published	2003-09-06
has exercises and real world examples. An emminently practical book.
Online bookstores carrying Refactoring Workbook abe books anz abe books.ca abe books.de amazon.ca amazon.de Chapters Indigo amazon.es Chapters Indigo eBooks iberlibro.com abe books.com abe books.fr amazon.com amazon.fr Barnes & Noble abe books.it Nook at Barnes & Noble amazon.it Kobo junglee.com Google play abe books.co.uk O’Reilly Safari amazon.co.uk Powells other stores
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Book referral for Refactoring: Improving the Design of Existing Code

	recommend book⇒Refactoring: Improving the Design of Existing Code
	by	Martin Fowler, Kent Beck [Contributor], John Brant [Contributor], William Opdyke, Don Roberts	978-7-50831554-6	paperback
	birth	1963 age:54	978-0-201-48567-7	hardcover
	publisher	Addison-Wesley	B000OZ0N4Y	kindle
	published	1999-07-08
Discusses how reorganising code into standard patterns makes it easier to maintain. Highly recommended. Practical before and after examples of cleaning up stinking code.
Online bookstores carrying Refactoring: Improving the Design of Existing Code abe books anz abe books.ca abe books.de amazon.ca amazon.de Chapters Indigo amazon.es Chapters Indigo eBooks iberlibro.com abe books.com abe books.fr amazon.com amazon.fr Barnes & Noble abe books.it Nook at Barnes & Noble amazon.it Kobo junglee.com Google play abe books.co.uk O’Reilly Safari amazon.co.uk Powells other stores
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Book referral for Code Complete: A Practical Handbook of Software Construction

	recommend book⇒Code Complete: A Practical Handbook of Software Construction
	by	Steve McConnell	978-1-55615-484-3	paperback
	publisher	Microsoft	978-0-7356-3697-2	eBook
	published	1993-05-14
Gives lots of practical advice on optimising. He talks mostly about C with examples in Fortran, Pascal, Basic and Ada. He doesn’t talk about Java. It didn’t exist when the book was written.
Online bookstores carrying Code Complete: A Practical Handbook of Software Construction abe books anz abe books.ca abe books.de amazon.ca amazon.de Chapters Indigo amazon.es Chapters Indigo eBooks iberlibro.com abe books.com abe books.fr amazon.com amazon.fr Barnes & Noble abe books.it Nook at Barnes & Noble amazon.it Kobo junglee.com Google play abe books.co.uk O’Reilly Safari amazon.co.uk Powells other stores
Greyed out stores probably do not have the item in stock. Try looking for it with a bookfinder.