In some snippets, I noticed that the array is initialized by casting the null value to String array like:
String[] array = (String[])null;
Generally, null is used to initialize variables e.g. an array of strings like:
String[] array = null;
When or why should I cast null values to string array or any other data type like this?
There is no need to use
String[] array = (String[]) null;
You might have to use (String[]) null if you pass a null value to an overloaded method (i.e. one of multiple methods having the same name) and you want the method that accepts a String[] argument to be chosen by the compiler.
For example, if you have the following methods :
public void doSomething (Integer i) {}
public void doSomething (String s) {}
public void doSomething (String[] arr) {}
Calling doSomething (null) will not pass compilation, since the compiler won't know which method to choose.
Calling doSomething ((String[]) null) will execute the 3rd method.
Of course, you can assign the null to a String[] variable, and avoid the casting :
String[] arr = null;
doSomething (arr);
public void doSomethingElse(String... values) - if passing null is not possible to distinct between values being null, or its first element being null
nullin te first place! Doing so will force you to do null checks later which are not needed otherwise.