Reflection - Beginning Java 8 Language Features - page 78

Table 3-2. Class Literals for Primitive Data Types and the void Keyword

Data Type Primitive Class Literal Wrapper Class Static Field

boolean boolean.class Boolean.TYPE

byte byte.class Byte.TYPE

char char.class Character.TYPE

short short.class Short.TYPE

int int.class Integer.TYPE

long long.class Long.TYPE

float float.class Float.TYPE

double double.class Double.TYPE

void void.class Void.TYPE

The Object class has a getClass() method, which returns the reference to the Class object of the class of the
object. This method is available in every class in Java because every class in Java, explicitly or implicitly, inherits
Object class. The method is declared final , so no descendant class can override it. For example, if you have testRef
as a reference to an object of class Test , you can get the reference to the Class object of the Test class as follows:

Test testRef = new Test();
Class<Test> testClass = testRef.getClass();

The Class class has a forName() static method which returns a reference to a Class object. It is an overloaded
method The declarations of the two overloaded versions of this method are

Class<?> forName(String className) •

Class<?> forName(String name, boolean initialize, ClassLoader loader)
The first version of the forName() method takes an argument, which is the fully qualified name of the class to
be loaded. It loads the class, initializes it, and returns the reference to its Class object. If the class is already loaded,
it simply returns the reference to the Class object of that class. The second version of this method gives you the
option to initialize or not to initialize the class when it is loaded, and which class loader should load the class. Both
methods throw a ClassNotFoundException if the class could not be loaded. To load a class named pkg1.Test , you
would write

•

Class testClass = Class.forName("pkg1.Test");

To get a Class object reference using the Class.forName() method, you do not have to know the name of the
class until runtime. The forName(String className) method initializes the class if it is not already initialized,
whereas the use of a class literal does not initialize the class. Prior to Java 5, a class was initialized when you used its
class literal. Java 5 does not initialize the class when you use its class literal. When a class is initialized, all its static
initializers are executed and all static fields are initialized. Listing 3-1 lists a Bulb class with only one static initializer,
which prints a message on the console. Listing 3-2 uses various methods to load and initialize the Bulb class.