Java ClassNotFoundException

Introduction

ClassNotFoundException in Java is a checked exception that occurs when an application tries to load a class through its name but cannot find the class definition. It helps identify class loading issues in your code.

Table of Contents

  1. What is ClassNotFoundException?
  2. Common Causes
  3. Handling ClassNotFoundException
  4. Examples of ClassNotFoundException
  5. Conclusion

1. What is ClassNotFoundException?

ClassNotFoundException is thrown when an application tries to load a class using Class.forName(), ClassLoader.loadClass(), or similar methods, but the class is not found in the classpath.

2. Common Causes

  • The class file is not in the classpath.
  • Incorrect class name or package name.
  • Classpath misconfiguration.

3. Handling ClassNotFoundException

To handle ClassNotFoundException, ensure that the class name and package are correct, and that the class file is in the classpath. Use a try-catch block to manage the exception gracefully.

4. Examples of ClassNotFoundException

Example: Loading a Class Dynamically

This example demonstrates handling a ClassNotFoundException when trying to load a class dynamically.

public class ClassNotFoundExceptionExample { public static void main(String[] args) { try { Class<?> cls = Class.forName("com.example.NonExistentClass"); } catch (ClassNotFoundException e) { System.out.println("Error: Class not found."); } } } 

Output:

Error: Class not found. 

Conclusion

ClassNotFoundException is an important mechanism in Java for identifying issues with class loading. By properly handling this exception and ensuring the correct configuration of the classpath, you can prevent class loading errors and maintain robust code.

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