What are Checked vs Unchecked Exceptions in Java?
In Java, exceptions are part of the Throwable hierarchy and are used to signal abnormal situations during the execution of a program. Understanding how exceptions are structured helps in designing more robust and readable code.
At the top of the hierarchy is the Throwable class, which has two direct subclasses:
Error: Serious problems that applications should not try to catch (e.g.,OutOfMemoryError,StackOverflowError).Exception: Conditions that applications might want to catch.
Checked Exceptions
Checked exceptions are exceptions that must be declared in a method or constructor’s throws clause if they can be thrown and not caught within the method. These exceptions are checked at compile time.
Examples:
IOExceptionSQLExceptionParseException
public static String getContentFromResource(String resourceName) {
try {
InputStream stream = ResourceUtils.class.getResourceAsStream(resourceName);
return StreamUtils.copyToString(stream, Charset.forName("UTF-8"));
} catch (IOException e) {
throw new RuntimeException(e);
}
}If you forget to handle a checked exception, the compiler will raise an error.
When to use?
When the failure is expected (e.g., I/O issues or database access problems).
Unchecked Exceptions
Unchecked exceptions are not required to be declared or handled, and are checked at runtime. They extend RuntimeException.
Examples:
NullPointerExceptionIllegalArgumentExceptionIndexOutOfBoundsException
public void divide(int a, int b) {
int result = a / b; // Can throws ArithmeticException (unchecked)
}When to use?
When the failure indicates a programming error or incorrect use of the API.
Conclusion
Understanding the exception hierarchy helps you make more informed decisions about how your code should respond to failures. When choosing between checked and unchecked exceptions, consider the type of error and whether it can (or should) be recovered from.
