Exceptions in Java

Exceptions in Java are events that disrupt the normal flow of a program's execution. They are used to handle errors and other exceptional events that may occur during runtime. Types of Exceptions Checked Exceptions (compile-time exceptions) Must be declared or handled (using try-catch or throws) Examples: IOException, SQLException, ClassNotFoundException Unchecked Exceptions (runtime exceptions) Not checked at compile time Examples: NullPointerException, ArrayIndexOutOfBoundsException, ArithmeticException Errors Serious problems that applications should not try to catch Examples: OutOfMemoryError, StackOverflowError Exception Handling Keywords try: Block of code to monitor for exceptions catch: Block that handles the exception finally: Block that always executes (for cleanup) throw: Used to explicitly throw an exception throws: Declares exceptions that might be thrown by a method Example try { // Code that might throw an exception int result = 10 / 0; // This will throw ArithmeticException } catch (ArithmeticException e) { System.out.println("Cannot divide by zero!"); } catch (Exception e) { System.out.println("General exception caught"); } finally { System.out.println("This will always execute"); } Custom Exceptions You can create your own exception classes by extending Exception (checked) or RuntimeException (unchecked): class MyCustomException extends Exception { public MyCustomException(String message) { super(message); } } Best Practices Catch specific exceptions rather than general Exception Don't ignore caught exceptions (empty catch blocks) Use finally blocks for resource cleanup Document exceptions with @throws in JavaDoc Consider whether to handle, propagate, or convert exceptions Would you like more details on any specific aspect of Java exceptions?

May 5, 2025 - 16:06

Exceptions in Java are events that disrupt the normal flow of a program's execution. They are used to handle errors and other exceptional events that may occur during runtime.

Types of Exceptions

Checked Exceptions (compile-time exceptions)
- Must be declared or handled (using try-catch or throws)
- Examples: IOException, SQLException, ClassNotFoundException
Unchecked Exceptions (runtime exceptions)
- Not checked at compile time
- Examples: NullPointerException, ArrayIndexOutOfBoundsException, ArithmeticException
Errors
- Serious problems that applications should not try to catch
- Examples: OutOfMemoryError, StackOverflowError

Exception Handling Keywords

try: Block of code to monitor for exceptions
catch: Block that handles the exception
finally: Block that always executes (for cleanup)
throw: Used to explicitly throw an exception
throws: Declares exceptions that might be thrown by a method

Example

try {
    // Code that might throw an exception
    int result = 10 / 0; // This will throw ArithmeticException
} catch (ArithmeticException e) {
    System.out.println("Cannot divide by zero!");
} catch (Exception e) {
    System.out.println("General exception caught");
} finally {
    System.out.println("This will always execute");
}

Custom Exceptions

You can create your own exception classes by extending Exception (checked) or RuntimeException (unchecked):

class MyCustomException extends Exception {
    public MyCustomException(String message) {
        super(message);
    }
}

Best Practices

Catch specific exceptions rather than general Exception
Don't ignore caught exceptions (empty catch blocks)
Use finally blocks for resource cleanup
Document exceptions with @throws in JavaDoc
Consider whether to handle, propagate, or convert exceptions

Would you like more details on any specific aspect of Java exceptions?