On Day 3, “Working with Objects,” you learned how to create Class objects that represent the class to which an object belongs. Every object in Java inherits the getClass() method, which identifies the class or interface of that object. The following statement creates a Class object named keyclass from an object referred to by the variable key:
Class keyClass = key.getClass();
By calling the getName() method of a Class object, you can find out the name of the class:
String keyName = keyClass.getName();
These features are part of Java’s support for reflection, a technique that enables one Java class—such as a program you write—to learn details about any other class. Through reflection, a Java program can load a class it knows nothing about; find the variables, methods, and constructors of that class; and work with them.
One use of reflection is to determine a serialized object’s class when it is read. Inspecting and Creating Classes The Class class, which is part of the java.lang package, is used to learn about and create classes, interfaces, and even primitive types. In addition to using getClass(), you can create Class objects by appending .class to the name of a class, interface, array, or primitive type, as in the following examples:
Class keyClass = KeyClass.class;
Class thr = Throwable.class;
Class floater = float.class;
Class floatArray = float[].class;
