Class<?>
- Java course
- Advanced
- Lesson 25/82
- 5 min
Learn class metadata with Class<?>.
The Class<?> object
Every type in Java has a Class<?> object; this object carries the type's information (fields, methods, constructors). Reflection starts here.
Three common paths: obj.getClass() gives the instance's class, String.class is the class literal, and Class.forName("java.lang.String") looks up the class object by name. All three return the same Class object; the choice depends on context.
Inspecting a Class
A Class object reveals a lot: getName returns the fully qualified name, getSimpleName the short name, getModifiers the access flags.
Example: c.getName() returns the full name like java.lang.String; c.getSimpleName() returns just String. These methods are used to inspect types at runtime; for example a framework that wants to log class names uses them directly.
Practice Print a class's fully qualified name
Get the Class object for String using Class.forName("java.lang.String"). Print the full name using getName() with System.out.println. Add throws ClassNotFoundException to main.
Starter code
// Find the String class with Class.forName
// Get the full name with getName
// Add throws ClassNotFoundException and printSample solution
public class ReflectionName {
public static void main(String[] args) throws ClassNotFoundException {
Class<?> c = Class.forName("java.lang.String");
System.out.println(c.getName());
}
}Expected output
java.lang.String
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which method finds a class by its fully qualified name?
- Class.forName Correct answer
- getClass
- getFields
- getMethod
Explanation: Class.forName interprets a string as a class name.
2 Complete the Class.forName call
Class<?> c = Class.____("java.lang.String");Class<?> c = Class.forName("java.lang.String");Explanation: forName interprets a string as a class name.
3 Match the ways to obtain a Class
| Term | Meaning |
|---|---|
obj.getClass() |
Instance's class |
String.class |
Class literal |
Class.forName |
Find by name |
getName |
Full name |