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Key existence check in HashMap
... return null;
}
Just check if the return value for get() is different from null.
This is the HashMap source code.
Resources :
HashMap source code Bad one
HashMap source code Good one
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How to print an exception in Python?
...the sys.exc_info() function and the traceback.print_exc() function gets it from there. You’d only ever need to pass in an exception explicitly when not handling an exception or when you want to show info based on a different exception.
– Martijn Pieters♦
Oc...
How can I add a key/value pair to a JavaScript object?
...ssign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.
Live example
var obj = {key1: "value1", key2: "value2"};
Object.assign(obj, {key3: "value3"});
document.body.innerHTML = JSON.stringi...
How do I call a dynamically-named method in Javascript?
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Since this post is from '09 you probably know this by now, but you're creating an array, then assigning to the array's properties (not indexes). You might as well do var dyn_functions = {}; so you don't needlessly create an array... this isn't ...
What is a covariant return type?
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From the release of JDK 1.5, covariant types were introduced in Java. and I'll explain it to you with a simple case, : When we override a function the function is allowed to make changes to it's behaviour that's what you get ...
What's the difference between using CGFloat and float?
...a double on 64-bit systems. However, the decision to do that was inherited from OS X, where it was made based on the performance characteristics of early PowerPC CPUs. In other words, you should not think that float is for 32-bit CPUs and double is for 64-bit CPUs. (I believe, Apple's ARM processors...
How can I grep for a string that begins with a dash/hyphen?
...t echos all the arguments. I use a script called echo-args.sh to play with from time to time, all it contains is:
echo $*
I invoke it as:
bash echo-args.sh \-X
bash echo-args.sh \\-X
bash echo-args.sh "\-X"
You get the idea.
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How do I get the find command to print out the file size with the file name?
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find . -name '*.ear' -exec ls -lh {} \;
just the h extra from jer.drab.org's reply. saves time converting to MB mentally ;)
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The provided URI scheme 'https' is invalid; expected 'http'. Parameter name: via
...; I was having the same issue and changing the <security> tag's mode from the default of "None" to "Transport" fixed it.
– Otis
Apr 7 '11 at 23:29
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How do I update/upsert a document in Mongoose?
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From the docs: "... when using the findAndModify helpers, the following are not applied: defaults, setters, validators, middleware" mongoosejs.com/docs/api.html#model_Model.findOneAndUpdate
– kellen
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