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Java Singleton and Synchronization
...e loaded when it is needed. That means that the first time getInstance is called, InstanceHolder will be loaded and instance will be created, and since this is controlled by ClassLoaders, no additional synchronization is necessary.
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How can I extract embedded fonts from a PDF as valid font files?
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You have several options. All these methods work on Linux as well as on Windows or Mac OS X. However, be aware that most PDFs do not include to full, complete fontface when they have a font embedded. Mostly they include just the subset of glyphs used ...
What is Android keystore file, and what is it used for?
... going to use "push data" in your app!
– KapteinMarshall
Sep 4 '13 at 9:43
Is Keystore machine specific ? Or we can u...
Google Docs/Drive - number the headings
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If you want something more easy, there is a Google Add-On called "Table of Contents" that will allow you to number your headings.
To install this add-on:
Click on the Add-Ons > Get Add-Ons.
Click on the "Table of Contents" icon or search for this addon to install it
The...
How do I use $scope.$watch and $scope.$apply in AngularJS?
...cycle and $scope
First and foremost, AngularJS defines a concept of a so-called digest cycle. This cycle can be considered as a loop, during which AngularJS checks if there are any changes to all the variables watched by all the $scopes. So if you have $scope.myVar defined in your controller and th...
Mysql error 1452 - Cannot add or update a child row: a foreign key constraint fails
...d FROM sourcecodes) should help to get rid of those IDs. Or if null is not allowed in sourcecode_id, then remove those rows or add those missing values to the sourcecodes table.
– naXa
Feb 23 '16 at 14:28
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How to load a UIView using a nib file created with Interface Builder
...ing a bit elaborate, but something that should be possible. So here is a challenge for all you experts out there (this forum is a pack of a lot of you guys :) ).
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Undo git update-index --assume-unchanged
... Minor improvement to your grep statement, it could use '^[a-z]' to catch all ignored files, since the first letter tag could be letters other than 'H'/'h'. From git-scm.com/docs/git-ls-files: This option identifies the file status with the following tags (followed by a space) at the start of eac...
How can I check if a single character appears in a string?
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But there's always a loop behind that call because you can't find a symbol otherwise.
– vava
Feb 3 '09 at 6:25
5
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MongoDB: How to query for records where field is null or not set?
...ount({sent_at: {$exists: false}})
If its there and null, or not there at all:
db.emails.count({sent_at: null})
Refer here for querying and null
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