Java Reference
In-Depth Information
methodonanobjectreference;forexample, Employee e = new Employee();
Class<? extends Employee> clazz = e.getClass(); . The
getClass() method does not throw an exception because the class from which the
object was created is already present in memory.
There is one more way to obtain a Class object, and that is to employ a class
literal ,whichisanexpressionconsistingofaclassname,followedbyaperiodseparator,
followed by reserved word class . Examples of class literals include Class<Em-
ployee> clazz = Employee.class; and Class<String> clazz =
String.class .
Perhaps you are wondering about how to choose between forName() ,
getClass() , and a class literal. To help you make your choice, the following list
compares each competitor:
forName() isveryflexibleinthatyoucandynamicallyspecifyanyreference
type by its package-qualified name. If the type is not in memory, it is loaded,
linked, and initialized. However, lack of compile-time type safety can lead to
runtime failures.
getClass() returns a Class object describing the type of its referenced
object. If called on a superclass variable containing a subclass instance, a
Class objectrepresentingthesubclasstypeisreturned.Becausetheclassisin
memory, type safety is assured.
• Aclassliteralreturnsa Class objectrepresentingitsspecifiedclass.Classlit-
the source code when it cannot locate the literal's specified class.
Note You can use class literals with primitive types, including void . Examples
include int.class , double.class , and void.class . The returned Class
object represents the class identified by a primitive type wrapper class's TYPE field
or java.lang.Void.TYPE . For example, each of int.class == In-
teger.TYPE and void.class == Void.TYPE evaluates to true.
You can also use class literals with primitive type-based arrays. Examples include
int[].class and double[].class . For these examples, the returned Class
objects represent Class<int[]> and Class<double[]> .
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