Conversions and Promotions - The Java Language Specification - page 89

• From type long to type Long
• From type float to type Float
• From type double to type Double
• From the null type to the null type
This rule is necessary because the conditional operator (§ 15.25 ) applies boxing
conversion to the types of its operands, and uses the result in further calcula-
tions.
At run time, boxing conversion proceeds as follows:
• If p is a value of type boolean , then boxing conversion converts p into a reference r
of class and type Boolean , such that r .booleanValue() == p
• If p is a value of type byte , then boxing conversion converts p into a reference r of
class and type Byte , such that r .byteValue() == p
• If p is a value of type char , then boxing conversion converts p into a reference r of
class and type Character , such that r .charValue() == p
• If p is a value of type short , then boxing conversion converts p into a reference r of
class and type Short , such that r .shortValue() == p
• If p is a value of type int , then boxing conversion converts p into a reference r of
class and type Integer , such that r .intValue() == p
• If p is a value of type long , then boxing conversion converts p into a reference r of
class and type Long , such that r .longValue() == p
• If p is a value of type float then:
♦ If p is not NaN, then boxing conversion converts p into a reference r of class
and type Float , such that r .floatValue() evaluates to p
♦ Otherwise, boxing conversion converts p into a reference r of class and type
Float such that r .isNaN() evaluates to true
• If p is a value of type double , then:
♦ If p is not NaN, boxing conversion converts p into a reference r of class and
type Double , such that r .doubleValue() evaluates to p
♦ Otherwise, boxing conversion converts p into a reference r of class and type
Double such that r .isNaN() evaluates to true
• If p is a value of any other type, boxing conversion is equivalent to an identity con-
version (§ 5.1.1 ) .