| Types java app |
|---|
| Data Types and Operators |
|---|
| (Primitive Data Types) |
|---|
| (Non-Primitive Data Types) |
|---|
| Control Flow Statements |
|---|
| Conditional Statements |
|---|
| Looping Statements |
|---|
| Branching Statements |
|---|
| Object-Oriented Programming (OOP) |
|---|
| Classes and Objects |
|---|
| Inheritance |
|---|
| Polymorphism |
|---|
| Encapsulation |
|---|
| Abstraction |
|---|
| Exception Handling |
|---|
| Introduction to Exceptions |
|---|
| Collections Framework |
|---|
| Overview of Collections |
|---|
| Commonly Used Collections |
|---|
| Iterators |
|---|
| Java I/O |
|---|
| File Handling |
|---|
| Serialization |
|---|
| Multithreading |
|---|
| Introduction to Threads |
|---|
| Thread Synchronization |
|---|
| GUI Programming with Swing |
|---|
| Introduction to Swing |
|---|
| Event Handling |
|---|
| Advanced Topics |
|---|
| Java Database Connectivity (JDBC) |
|---|
| JAVA CODE |
|---|
|
Java Basics
|
|
Working with Objects
|
|
Arrays, Conditionals, and Loops
|
|
Creating Classes and Applications in Java
|
|
More About Methods
|
|
Java Applet Basics
|
|
Graphics, Fonts, and Color
|
|
Simple Animation and Threads
|
|
More Animation, Images, and Sound
|
|
Managing Simple Events and Interactivity
|
|
Creating User Interfaces with the awt
|
|
Windows, Networking, and Other Tidbits
|
|
Modifiers, Access Control, and Class Design
|
|
Packages and Interfaces
|
|
Exceptions
|
|
Multithreading
|
|
Streams and I/O
|
|
Using Native Methods and Libraries
|
|
Under the Hood
|
|
Java Programming Tools
|
|
Working with Data Structures in Java
|
|
Advanced Animation and Media
|
|
Fun with Image Filters
|
|
Client/Server Networking in Java
|
|
Emerging Technologies
|
|
appendix A :- Language Summary
|
|
appendix B :- Class Hierarchy Diagrams
|
|
appendix C The Java Class Library
|
|
appendix D Bytecodes Reference
|
|
appendix E java.applet Package Reference
|
|
appendix F java.awt Package Reference
|
|
appendix G java.awt.image Package Reference
|
|
appendix H java.awt.peer Package Reference
|
|
appendix I java.io Package Reference
|
|
appendix J java.lang Package Reference
|
|
appendix K java.net Package Reference
|
|
appendix L java.util Package Reference
|
Creating custom exceptions in Java is a powerful feature that allows developers to handle errors in a more controlled and meaningful way. Custom exceptions can provide more specific error information and enable cleaner, more readable code. Here’s a detailed explanation of creating custom exceptions in Java, including examples and best practices.
Understanding Exceptions in Java
In Java, exceptions are events that disrupt the normal flow of a program’s execution. Exceptions are objects that represent an error or unexpected behavior and can be thrown and caught during the program’s execution.
Java exceptions are categorized into three types:
- Checked Exceptions: These exceptions are checked at compile time. The programmer must handle these exceptions using a try-catch block or declare them using the
throwskeyword. Examples includeIOException,SQLException. - Unchecked Exceptions: These exceptions are not checked at compile time. They include
RuntimeExceptionand its subclasses, likeNullPointerException,IndexOutOfBoundsException. - Errors: These are serious issues that a program should not try to catch, such as
OutOfMemoryError,StackOverflowError.
Creating Custom Exceptions
To create a custom exception, you can extend either Exception (for checked exceptions) or RuntimeException (for unchecked exceptions). Here’s how to do it:
Step-by-Step Guide
Define the Custom Exception Class:
- Extend
Exceptionfor checked exceptions orRuntimeExceptionfor unchecked exceptions. - Provide constructors that call the superclass constructors.
- Optionally, override methods like
toString()to provide a custom string representation.
- Extend
Use the Custom Exception:
- Throw the custom exception where appropriate.
- Catch the custom exception in the appropriate place in your code.
Example: Creating a Checked Custom Exception
// Custom checked exception
public class CustomCheckedException extends Exception {
public CustomCheckedException() {
super();
}
public CustomCheckedException(String message) {
super(message);
}
public CustomCheckedException(String message, Throwable cause) {
super(message, cause);
}
public CustomCheckedException(Throwable cause) {
super(cause);
}
}
// Usage in a method
public class Example {
public void riskyMethod() throws CustomCheckedException {
if (/* some condition */) {
throw new CustomCheckedException("An error occurred in riskyMethod");
}
}
public static void main(String[] args) {
Example example = new Example();
try {
example.riskyMethod();
} catch (CustomCheckedException e) {
System.out.println(e.getMessage());
}
}
}
Example: Creating an Unchecked Custom Exception
// Custom unchecked exception
public class CustomUncheckedException extends RuntimeException {
public CustomUncheckedException() {
super();
}
public CustomUncheckedException(String message) {
super(message);
}
public CustomUncheckedException(String message, Throwable cause) {
super(message, cause);
}
public CustomUncheckedException(Throwable cause) {
super(cause);
}
}
// Usage in a method
public class Example {
public void riskyMethod() {
if (/* some condition */) {
throw new CustomUncheckedException("An error occurred in riskyMethod");
}
}
public static void main(String[] args) {
Example example = new Example();
try {
example.riskyMethod();
} catch (CustomUncheckedException e) {
System.out.println(e.getMessage());
}
}
}
Best Practices for Custom Exceptions
- Use Meaningful Names: The exception name should clearly indicate the problem, making the code more readable and maintainable.
- Include Descriptive Messages: Provide detailed error messages to help diagnose issues quickly.
- Use Custom Exceptions Judiciously: Avoid creating too many custom exceptions. Use them when they add significant value over standard exceptions.
- Document Custom Exceptions: Document when and why the custom exception should be thrown and how it should be handled.
By following these guidelines, you can create custom exceptions that enhance the clarity and robustness of your Java applications.
