Checked vs Unchecked Exception: Difference and Comparison

Checking for exceptions is one of the most important things in programming and software testing. Checked And Unchecked Exception stops the program from running when it is trying to catch a bug or error.

Moreover, it is considered as it is the programmer’s responsibility to make sure these errors never happen. Both Checked and Unchecked Exceptions are exceptionally similar, yet they are different.

Key Takeaways

1. The compiler checks checked exceptions during compile-time and need to be handled by the programmer using the try-catch block or throws keyword, whereas unchecked exceptions occur at runtime and do not need to be handled.
2. Checked exceptions are used for recoverable errors, such as file not found, while unchecked exceptions are used for unrecoverable errors, such as out-of-memory or null pointer exceptions.
3. Checked exceptions are part of the method’s signature, while unchecked exceptions are not.

Checked vs Unchecked Exception

The difference between Checked And Unchecked Exception is that Checked exceptions are those that must be caught and handled by the checks () statement or they will cause a program to terminate and print a stack trace, whereas, Unchecked exceptions, on the other hand, should not need to be caught or handled at all, as it is the programmer’s responsibility to make sure these errors never happen.

The Checked exception is a specific type of exception that stops the program from running until it is either caught by a catch block or specified in the throws clause of a method, moreover, Checked exception is caught and handled by the checks () statement, or they will cause a program to terminate and print a stack trace.

If the code that caused the exception was not tested properly, it could cause strange Unchecked exceptional bugs that can be difficult to find and fix.

Moreover, Unchecked exceptions should not need to be caught or handled at all, as it is the programmer’s responsibility to make sure these errors never happen.

Comparison Table

Parameters of Comparison	Checked Exception	Unchecked Exception
Definition	Checked exceptions are those that must be caught and handled by the checks () statements.	Unchecked Exceptions should not need to be caught or handled at all.
Occurrence	A catch block must handle checked exceptions during compile time.	Uncaught exceptions, also known as runtime exceptions, are Unchecked Exceptions.
Error Handling	A checked Exception stops the program from running until it is trying to catch a bug or error.	It is the programmer’s responsibility to make sure these errors never happen.
Exception Classes	It does have exceptional classes.	It does not have any exceptional classes, or it is not a major part of exceptional classes.
Example	OutOfMemoryError, NullPointerException and StackOverflowError.	IndexOutOfBoundsException

What is Checked Exception?

Checked Exceptions are closely related to software testing, moreover, a checked exception is an exception that must be handled, or the program will terminate.

This means that code following a throw statement will not execute if no catch block handles the exception.

Checked exceptions serve two purposes: they stop the program from continuing when an error has occurred and provide debugging information about where to find that error.

The compiler does not force the programmer to handle the exception, but any class that extends another class should also either extend or implement all of its checked exceptions.

If it does not, a compilation of the extending class fails with a compile-time error stating that it must handle all of its superclass-checked exceptions. This prevents inheritance from being used to circumvent built-in failure modes.

When an exception is thrown, it is passed to the debugger in Eclipse or to the operating system, which then terminates the program normally. The operating system prints out a stack trace.

A stack trace provides information for each method call in the order they were called. This allows the programmer to find where in code or where in their code’s execution flow an exception occurred.

What is an Unchecked Exception?

Unchecked exceptions exist to allow programmers to program more flexibly and efficiently. Java has been designed to enable programmers to create applications that use resources efficiently and avoid the appearance of deadlock.

Unchecked exceptions can be eliminated by careful design and coding practices. However, all exceptions except NullPointerException in Java code are considered unchecked.

Unchecked exceptions should not need to be caught or handled at all.

Moreover, They are a way for higher-level code to tell lower-level code that it is going to do something that is not thread-safe but that will not cause problems if there is only one thread running at any given time, such as updating some data or rendering some graphics on the screen.

Using unchecked exceptions is a risky proposition. If a class is going to throw an unchecked exception, then whoever uses that class needs to be aware of it and have some rigorous methods in place for dealing with it.

For example, a programmer may want to read some data from a file and then write it back again, and this kind of functionality does not need any synchronization.

It’s perfectly acceptable for an application to read the same data twice on two different threads without having any negative effects on system performance or stability.

Main Differences Between Checked and Unchecked Exceptions

1. Checked Exceptions are those that must be caught and handled by the checks () statements, whereas, Unchecked Exceptions should not need to be caught or handled at all.
2. Checked Exceptions must be handled by a catch block during compile time, whereas Uncaught Exceptions, also known as runtime exceptions, are Unchecked Exceptions.
3. The checked Exception stops the program from running until it is trying to catch a bug or error, whereas, Unchecked Exceptions are the programmer’s responsibility to make sure these errors never happen.
4. Checked Exception does have exceptional classes, whereas, Unchecked Exceptions do not have any exceptional classes or it is not a major part of exceptional classes.
5. An example of a Checked Exception would be an OutOfMemoryError, NullPointerException, and StackOverflowError, whereas an example of an Unchecked Exception would be an IndexOutOfBoundsException.

References

1. https://ieeexplore.ieee.org/abstract/document/4343929/
2. https://link.springer.com/article/10.1023/A:1010020917337