Java primitive types (such as int , double , or float ) cannot have null values , which you must consider in choosing your result expression and host expression types.
Read moreHow do you check if an object is a double in Java?
As Java is a statically typed language, you always know if something is a double at compile time. That also means that the if statement is completely unnecessary. If the variable v is possibly of type Double (the wrapped type of double ) then you can simply use v instanceof Double to check.
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