Checks that the specified object reference is not null. This method is designed primarily for doing parameter validation in methods and constructors, [ This function is made for what you want to do: explicitly mark what is not to be null.
The benefit is that you find null -values right where they should not occur. You will have less troubles debugging problems caused by null s that are passed somewhere where they shouldn't be. Another benefit is the flexibility when using this function in contrast to assert. While assert is a keyword for checking a boolean value, Objects. Keep in mind that Objects. So assert has different purposes : primarily testing. It has to be enabled, so you can enable it for testing and disable it in production.
Use it to seperate testing-only-tests from tests, or rather checks, that are meant for production-code too. The most important thing to remember about assertions is that they can be disabled, so never assume they'll be executed.
For backward compatibility, the JVM disables assertion validation by default. They must be explicitly enabled using either the -enableassertions command line argument, or its shorthand -ea:. As assertions aren't enabled by default you can never assume they will be executed when used in the code. So you should always check for null values and empty Optionals, avoid using assertions to check inputs into a public method and instead use an unchecked exception In general do all the checks as if the assertion wasn't there.
Assertions are disabled by default if you just execute standalone jvm. When they are disabled, they have zero footprint, hence they will not affect your production application.
However, they are probably your best friends when developing and testing your code, and most of testing framework runners enable assertions JUnit does , so your assertion code is executed when you run your unit tests, helping you detect any potential bugs earlier e.
That said, as the other answer suggests, for exactly that reason they are not always enabled you cannot rely on assertions to do some vital checks, or especially! For an interesting example of how you could use asserts, have a look here - at the end of the file there's a method singleThreadedAccess which is called from the assert statement on line and is there to catch any potential multithreaded access in tests.
There are other libraries with their own Assert. It's also pretty simple to write your own. However, keep in mind what exceptions you throw if this is a web service. The previous method mentioned, for example, throws an IllegalArgumentException which by default in Spring returns a In the case of a web service, this is often not an internal server error, and should not be a , but rather a , which is a bad request. Do not use assert to catch something that might logically happen i.
Use assert only when the error is unrecoverable. Do not put any production logic in the code that runs when the assertion is checked. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked Related Software Engineering Stack Exchange is a question and answer site for professionals, academics, and students working within the systems development life cycle.
It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. In Java, which is more highly recommended, and why? Both types will throw exceptions, so in that regard handling them is the same. Assertions are removed at runtime unless you explicitly specify to "enable assertions" when compiling your code.
Java Assertions are not to be used on production code and should be restricted to private methods see Exception vs Assertion , since private methods are expected to be known and used only by the developers.
Also assert will throw AssertionError which extends Error not Exception , and which normally indicates you have a very abnormal error like "OutOfMemoryError" which is hard to recover from, isn't it? Remove the "enable assertions" flag, and check with a debugger and you'll see that you will not step on the IllegalArgumentException throw call I personally use the Spring Framework 's Assert class that has a few methods for checking arguments and that throw "IllegalArgumentException" on failure.
Basically, what you do is:. Which will in fact execute exactly the same code you wrote in your second example. There are a few other useful methods such as hasText , hasLength in there. Unchecked exceptions are designed to detect programming errors of the users of your library, while assertions are designed to detect errors in your own logic.
These are separate issues that should not be mixed. If you are writing a function that does not allow null as a valid parameter value, you should add the Nonnull annotation to the signature and use Objects. The Nonnull annotation is for documentation and will provide helpful warnings at compile time in some cases. It does not prevent null from being passed at runtime. Update: The Nonnull annotation is not part of the Java standard library. Instead, there are numerous competing standards from third party libraries see Which NotNull Java annotation should I use?
If you come across any mistakes or bugs, please email me to [email protected]. A Stream is an abstraction that either produces or consumes information. There are two types of Streams and they are: Byte Streams: Provide a convenient means for handling input and output of bytes. Character Streams classes are defined by using two abstract classes, namely Reader and Writer. The greatest obstacle to discovery is not ignorance; it is the illusion of knowledge.
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