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What is the difference between == and equals() in Java?
...r to your question is "yes", but...
.equals(...) will only compare what it is written to compare, no more, no less.
If a class does not override the equals method, then it defaults to the equals(Object o) method of the closest parent class that has overridden this method.
If no parent classes ha...
Linux: copy and create destination dir if it does not exist
...nd (or probably an option to cp) that creates the destination directory if it does not exist.
21 Answers
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Performance differences between debug and release builds
I must admit, that usually I haven't bothered switching between the Debug and Release configurations in my program, and I have usually opted to go for the Debug configuration, even when the programs are actually deployed at the customers place.
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Is it secure to store passwords as environment variables (rather than as plain text) in config files
I work on a few apps in rails, django (and a little bit of php), and one of the things that I started doing in some of them is storing database and other passwords as environment variables rather than plain text in certain config files (or in settings.py, for django apps).
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ALTER TABLE without locking the table?
...ySQL, the whole table is read-locked (allowing concurrent reads, but prohibiting concurrent writes) for the duration of the statement. If it's a big table, INSERT or UPDATE statements could be blocked for a looooong time. Is there a way to do a "hot alter", like adding a column in such a way that th...
Textarea that can do syntax highlighting on the fly?
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It's not possible to achieve the required level of control over presentation in a regular textarea.
If you're OK with that, try CodeMirror or Ace (formerly skywriter and bespin), or Monaco (used in MS VSCode).
From the dupl...
SQL JOIN - WHERE clause vs. ON clause
After reading it, this is not a duplicate of Explicit vs Implicit SQL Joins .
The answer may be related (or even the same) but the question is different.
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Can two applications listen to the same port?
...lications on the same machine bind to the same port and IP address? Taking it a step further, can one app listen to requests coming from a certain IP and the other to another remote IP?
I know I can have one application that starts off two threads (or forks) to have similar behavior, but can two ap...
When and how should I use a ThreadLocal variable?
... object (I'm looking at you, SimpleDateFormat). Instead, give each thread its own instance of the object.
For example:
public class Foo
{
// SimpleDateFormat is not thread-safe, so give one to each thread
private static final ThreadLocal<SimpleDateFormat> formatter = new ThreadLocal...
How to check for valid email address? [duplicate]
Is there a good way to check a form input using regex to make sure it is a proper style email address? Been searching since last night and everybody that has answered peoples questions regarding this topic also seems to have problems with it if it is a subdomained email address.
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