Making Steaks from Sacred Cows
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Transcript of Making Steaks from Sacred Cows
© BBC
I see Keep Out signs
as suggestions more
than actual orders.
Like Dry Clean Only.
Cargo cult programming is a style of computer programming characterized by the ritual inclusion of code or program structures that serve no real purpose.
Cargo cult programming can also refer to the results of applying a design pattern or coding style blindly without understanding the reasons behind that design principle.
http://en.wikipedia.org/wiki/Cargo_cult_programming
Une Idée
Rien n'est plus
dangereux qu'une
idée, quand on n'a
qu'une idée.
Émile-Auguste Chartier
Nothing is more
dangerous than an
idea, when you have
only one idea.
Émile-Auguste Chartier
Nothing is more
dangerous than an
IDE, when you have
only one IDE.
I currently have an average of 15-25 imports in each source file, which is seriously making my code mixed-up and confusing.
Is too many imports in your code a bad thing?
Is there any way around this?
http://stackoverflow.com/questions/8485689/too-many-imports-spamming-my-code
It's normal in Java world to have a lot of imports.
Not importing whole packages is good practice.
It's a good practice to import class by class instead of importing whole packages.
http://stackoverflow.com/questions/8485689/too-many-imports-spamming-my-code
Why?
It is not a problem. Any IDE will manage imports and show them to you only when needed.
Most IDEs support code folding where all the imports are folded down to one line. I rarely even see my imports these days as the IDE manages them and hides them as well.
Any good IDE, such as Eclipse, will collapse the imports in one line, and you can expand them when needed, so they won't clutter your view.
http://stackoverflow.com/questions/8485689/too-many-imports-spamming-my-code
It is not a problem. Any IDE will manage imports and show them to you only when needed.
Most IDEs support code folding where all the imports are folded down to one line. I rarely even see my imports these days as the IDE manages them and hides them as well.
Any good IDE, such as Eclipse, will collapse the imports in one line, and you can expand them when needed, so they won't clutter your view.
http://stackoverflow.com/questions/8485689/too-many-imports-spamming-my-code
It is not a problem. Any IDE will manage imports and show them to you only when needed.
Most IDEs support code folding where all the imports are folded down to one line. I rarely even see my imports these days as the IDE manages them and hides them as well.
Any good IDE, such as Eclipse, will collapse the imports in one line, and you can expand them when needed, so they won't clutter your view.
http://stackoverflow.com/questions/8485689/too-many-imports-spamming-my-code
What is the Matrix?
Control.
The Matrix is a computer-generated
dream world built to keep us under
control in order to change a human
being into this.
© Warner Bros.
I currently have an average of 15-25 imports in each source file, which is seriously making my code mixed-up and confusing.
Yes?
Is too many imports in your code a bad thing?
Yes.
Is there any way around this?
Yes!
Avoid Long Import Lists by Using Wildcards
Long lists of imports are daunting to the reader.
We don't want to clutter up the tops of our
modules with 80 lines of imports. Rather we
want the imports to be a concise statement
about which packages we collaborate with.
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.*;
import java.beans.Introspector;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.beans.*;
import java.lang.reflect.*;
import java.util.*;
import java.awt.*;
import java.util.*;
List?
import java.awt.*;
import java.util.*;
import java.util.List;
Open–Closed Principle
The principle stated that a good module
structure should be both open and closed:
Closed, because clients need the
module's services to proceed with their
own development, and once they have
settled on a version of the module should
not be affected by the introduction of new
services they do not need.
Open, because there is no guarantee that
we will include right from the start every
service potentially useful to some client.
[...] A good module structure
should be [...] closed [...] because
clients need the module's
services to proceed with their
own development, and once
they have settled on a version of
the module should not be
affected by the introduction of
new services they do not need.
Published Interface is a term I used (first in Refactoring) to refer to a class interface that's used outside the code base that it's defined in.
Martin Fowler http://martinfowler.com/bliki/PublishedInterface.html
There is no problem changing a
method name if you have access to
all the code that calls that method.
Even if the method is public, as long
as you can reach and change all the
callers, you can rename the method.
There is a problem only if the
interface is being used by code that
you cannot find and change. When
this happens, I say that the interface
becomes a published interface (a
step beyond a public interface).
Published Interface is a term I used (first in Refactoring) to refer to a class interface that's used outside the code base that it's defined in.
The distinction between published and public is actually more important than that between public and private.
The reason is that with a non-published interface you can change it and update the calling code since it is all within a single code base. [...] But anything published so you can't reach the calling code needs more complicated treatment.
Martin Fowler http://martinfowler.com/bliki/PublishedInterface.html
[...] A good module structure
should be [...] open [...] because
there is no guarantee that we will
include right from the start every
service potentially useful to some
client.
extends
A myth in the object-oriented design
community goes something like this:
If you use object-oriented technology,
you can take any class someone else
wrote, and, by using it as a base class,
refine it to do a similar task.
Robert B Murray
C++ Strategies and Tactics
Design and implement for
inheritance or else prohibit it
By now, it should be apparent that
designing a class for inheritance places
substantial limitations on the class.
Bertrand Meyer gave us guidance as long ago as 1988 when he coined the now famous open-closed principle. To paraphrase him:
Software entites (classes, modules, functions, etc.) should be open for extension, but closed for modification.
Robert C Martin "The Open-Closed Principle"
C++ Report, January 1996
http://blog.8thlight.com/uncle-bob/2014/05/12/TheOpenClosedPrinciple.html
http://blog.8thlight.com/uncle-bob/2014/05/12/TheOpenClosedPrinciple.html
I've heard it said that the OCP is wrong, unworkable, impractical, and not for real programmers with real work to do. The rise of plugin architectures makes it plain that these views are utter nonsense. On the contrary, a strong plugin architecture is likely to be the most important aspect of future software systems.
public abstract class Shape
{
...
}
public class Square : Shape
{
...
public void DrawSquare() ...
}
public class Circle : Shape
{
...
public void DrawCircle() ...
}
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
if(s is Square)
(s as Square).DrawSquare();
else if(s is Circle)
(s as Circle).DrawCircle();
}
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
if(s is Square)
(s as Square).DrawSquare();
else if(s is Circle)
(s as Circle).DrawCircle();
}
public abstract class Shape
{
...
public abstract void Draw();
}
public class Square : Shape
{
...
public override void Draw() ...
}
public class Circle : Shape
{
...
public override void Draw() ...
}
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
s.Draw();
}
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
s.Draw();
}
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
s.Draw();
}
Bertrand Meyer gave us guidance as long ago as 1988 when he coined the now famous open-closed principle. To paraphrase him:
Software entites (classes, modules, functions, etc.) should be open for extension, but closed for modification.
Robert C Martin "The Open-Closed Principle"
C++ Report, January 1996
Bertrand Meyer gave us guidance as long ago as 1988 when he coined the now famous open-closed principle. To paraphrase him:
Software entites (classes, modules, functions, etc.) should be open for extension, but closed for modification.
Robert C Martin "The Open-Closed Principle"
C++ Report, January 1996
This double requirement looks like a
dilemma, and classical module
structures offer no clue.
This double requirement looks like a
dilemma, and classical module
structures offer no clue. But
inheritance solves it.
This double requirement looks like a
dilemma, and classical module
structures offer no clue. But
inheritance solves it. A class is
closed, since it may be compiled,
stored in a library, baselined, and
used by client classes. But it is also
open, since any new class may use
it as parent, adding new features.
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
if(s is Square)
(s as Square).DrawSquare();
else if(s is Circle)
(s as Circle).DrawCircle();
}
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
if(s is Square)
(s as Square).DrawSquare();
else if(s is Circle)
(s as Circle).DrawCircle();
}
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
s.Draw();
}
public abstract class Shape ...
public class Square : Shape ...
public class Circle : Shape ...
static void DrawAllShapes(Shape[] list)
{
foreach(Shape s in list)
s.Draw();
}
Don't publish
interfaces prematurely.
Modify your code
ownership policies to
smooth refactoring.
Constructors that throw
Do not throw from a constructor.
Do not throw from a constructor?
Immutable Value
The internal state of a value
object is set at construction
and no subsequent
modifications are allowed.
To some, the most important
aspect of exceptions is that they
provide a general mechanism for
reporting errors detected in a
constructor.
Bjarne Stroustrup
The Design and Evolution of C++
Naomi Epel The Observation Deck
Exceptional Naming
ClassNotFoundException
EnumConstantNotPresentException
IllegalArgumentException
IllegalAccessException
IndexOutOfBoundsException
NegativeArraySizeException
NoSuchMethodException
TypeNotPresentException
UnsupportedOperationException
ClassNotFound
EnumConstantNotPresent
IllegalArgument
IllegalAccess
IndexOutOfBounds
NegativeArraySize
NoSuchMethod
TypeNotPresent
UnsupportedOperation
ArithmeticException
ArrayStoreException
ClassCastException
InstantiationException
NullPointerException
SecurityException
Arithmetic
ArrayStore
ClassCast
Instantiation
NullPointer
Security
IntegerDivisionByZero
IllegalArrayElementType
CastToNonSubclass
ClassCannotBeInstantiated
NullDereferenced
SecurityViolation
Omit needless words.
William Strunk and E B White
The Elements of Style
Shoulda Woulda Coulda
public static bool IsLeapYear(int year) ...
[Test] public void TestIsLeapYear() ...
function test
test
test
method test
test
test
method
method
test
test
YearsNotDivisibleBy4...
YearsDivisibleBy4ButNotBy100...
YearsDivisibleBy100ButNotBy400...
YearsDivisibleBy400...
Years_not_divisible_by_4_...
Years_divisible_by_4_but_not_by_100_...
Years_divisible_by_100_but_not_by_400_...
Years_divisible_by_400_...
Years_not_divisible_by_4_should_not_be_leap_years
Years_divisible_by_4_but_not_by_100_should_be_leap_years
Years_divisible_by_100_but_not_by_400_should_not_be_leap_years
Years_divisible_by_400_should_be_leap_years
Years_not_divisible_by_4_are_not_leap_years
Years_divisible_by_4_but_not_by_100_are_leap_years
Years_divisible_by_100_but_not_by_400_are_not_leap_years
Years_divisible_by_400_are_not_leap_years
Years_not_divisible_by_4_are_not_leap_years
Years_divisible_by_4_but_not_by_100_are_leap_years
Years_divisible_by_100_but_not_by_400_are_not_leap_years
Years_divisible_by_400_are_not_leap_years
Years_not_divisible_by_4_are_not_leap_years
Years_divisible_by_4_but_not_by_100_are_leap_years
Years_divisible_by_100_but_not_by_400_are_not_leap_years
Years_divisible_by_400_are_not_leap_years
Propositions are vehicles for stating how things are or might be.
Thus only indicative sentences which it makes sense to think of as being true or as being false are capable of expressing propositions.
Make definite assertions. Avoid tame, colourless, hesitating, noncommittal language.
Note [...] that when a sentence is made stronger, it usually becomes shorter. Thus brevity is a by-product of vigour.
William Strunk and E B White
The Elements of Style