Operators and Expressions - The Java Programming Language - page 324

cause it is of type int an explicit cast must be used. This restric-
tion makes it easier to determine which method to invoke when
overloaded forms of it existfor example, if you try to pass a short
to a method that could take an int or a byte , should the short get
widened to an int , or narrowed to a byte ?
• Numeric promotion Numeric promotion, as discussed in Section
9.1 on page 201 , ensures that all the operands of an arithmetic
expression are of the appropriate type by performing widening
primitive conversions, preceded if necessary by unboxing conver-
sions.
• Casts Casts potentially allow for any of the conversions, but may
fail at runtimethis is discussed in the next section.
• String conversions String conversions occur when the string con-
catenation operation is used (see page 214 ) and are discussed
further in " String Conversions " on page 220 .
9.4.2. Explicit Type Casts
When one type cannot be assigned to another type with implicit conver-
sion, often it can be explicitly cast to the other typeusually to perform a
narrowing conversion. A cast requests a new value of a new type that is
the best available representation of the old value in the old type. Some
casts are not allowedfor example, a boolean cannot be cast to an int but
explicit casting can be used to assign a double to a long , as in this code:
double d = 7.99;
long l = (long) d;
When a floating-point value is cast to an integer, the fractional part is
lost by rounding toward zero; for instance, (int)-72.3 is -72 . Methods
available in the Math and StrictMath classes round floating-point values
to integers in other ways. See " Math and StrictMath " on page 657 for
details. A floating-point NaN becomes the integer zero when cast. Val-