The most likely reason for use of single vs. double in different libraries is programmer preference and/or API consistency. Other than being consistent, use whichever best suits the string.
Using the other type of quote as a literal:
alert('Say "Hello"');
alert("Say 'Hello'");
This can get complicated:
alert("It's \"game\" time.");
alert('It\'s "game" time.');
Another option, new in ECMAScript 6, is template literals which use the backtick character:
alert(`Use "double" and 'single' quotes in the same string`);
alert(`Escape the \` back-tick character and the \${ dollar-brace sequence in a string`);
Template literals offer a clean syntax for: variable interpolation, multi-line strings, and more.
Note that JSON is formally specified to use double quotes, which may be worth considering depending on system requirements.
The docs for java.io.Serializable
are probably about as good an explanation as you'll get:
The serialization runtime associates with each serializable class a version number, called a serialVersionUID
, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the object that has a different serialVersionUID
than that of the corresponding sender's class, then deserialization will result in an
InvalidClassException
. A serializable class can declare its own serialVersionUID
explicitly by declaring a field named serialVersionUID
that must be static, final, and of type long
:
ANY-ACCESS-MODIFIER static final long serialVersionUID = 42L;
If a serializable class does not explicitly declare a serialVersionUID
, then the serialization runtime will calculate a default serialVersionUID
value for that class based on various aspects of the class, as described in the Java(TM) Object Serialization Specification. However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID
values, since the default serialVersionUID
computation is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions
during deserialization. Therefore, to guarantee a consistent serialVersionUID
value across different java compiler implementations, a serializable class must declare an explicit serialVersionUID
value. It is also strongly advised that explicit serialVersionUID
declarations use the private modifier where possible, since such declarations apply only to the immediately declaring class — serialVersionUID
fields are not useful as inherited members.
Best Answer
This has (almost) nothing to do with string comparison. String interning is intended for saving memory if you have many strings with the same content in you application. By using
String.intern()
the application will only have one instance in the long run and a side effect is that you can perform fast reference equality comparison instead of ordinary string comparison (but this is usually not advisable because it is realy easy to break by forgetting to intern only a single instance).