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What is an example of the Liskov Substitution Principle?
... to model this with inheritance. However if in code you made Square derive from Rectangle, then a Square should be usable anywhere you expect a Rectangle. This makes for some strange behavior.
Imagine you had SetWidth and SetHeight methods on your Rectangle base class; this seems perfectly logical...
Unique BooleanField value in Django?
...if you've set the boolean to True, make sure all others are set to False.
from django.db import transaction
class Character(models.Model):
name = models.CharField(max_length=255)
is_the_chosen_one = models.BooleanField()
def save(self, *args, **kwargs):
if not self.is_the_chos...
Error java.lang.OutOfMemoryError: GC overhead limit exceeded
...ning only the garbage collection at all time.
To prevent your application from soaking up CPU time without getting anything done, the JVM throws this Error so that you have a chance of diagnosing the problem.
The rare cases where I've seen this happen is where some code was creating tons of tempor...
How do you make a web application in Clojure? [closed]
... I worked on Java projects, but not Java-the-world. I never made a web app from scratch in Java. If I have to do it with Python, Ruby, I know where to go (Django or Rails), but if I want to make a web application in Clojure, not because I'm forced to live in a Java world, but because I like the lang...
How does Activity.finish() work in Android?
...
Does it exits immediately or completes
the function from which it was called
?
The method that called finish() will run to completion. The finish() operation will not even begin until you return control to Android.
...
What's so wrong about using GC.Collect()?
...
From Rico's Blog...
Rule #1
Don't.
This is really the most important
rule. It's fair to say that most
usages of GC.Collect() are a bad idea
and I went into that in some detail in
the orginal posting so I won't repeat
all th...
Why is there no multiple inheritance in Java, but implementing multiple interfaces is allowed?
...Containing more than one subobject of same base class, ambiguity (override from which base class use), complicated rules of resolving such ambiguity.
– Tadeusz Kopec
May 22 '13 at 7:54
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What is Common Gateway Interface (CGI)?
...is a "common" gateway interface for everything. It is so trivial and naive from the name. I feel that I understood this and I felt this every time I encountered this word. But frankly, I didn't. I'm still confused.
...
Create a new cmd.exe window from within another cmd.exe prompt
...
You can just type these 3 commands from command prompt:
start
start cmd
start cmd.exe
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How to assign a Git SHA1's to a file without Git?
...3fae03f4606ea9991df8befbb2fca795e648fa
Here is a Python implementation:
from hashlib import sha1
def githash(data):
s = sha1()
s.update("blob %u\0" % len(data))
s.update(data)
return s.hexdigest()
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