What is the difference between @Before, @BeforeClass, @After, and @AfterClass annotations in JUnit?

The @Before annotation in JUnit is used to signal that the annotated method should be executed before each test method in the class. This annotation is typically used for setting up common test fixtures or initializing resources before the actual test execution.

The @BeforeClass annotation is used to specify that the annotated method should be run once before any of the test methods in the class are executed. This is useful for setting up resources that are shared across all the test methods in the class.

On the other hand, the @After annotation signals that the annotated method should be run after each test method. It is commonly used for cleaning up resources or releasing any acquired test fixtures after the test execution.

Lastly, the @AfterClass annotation is similar to @BeforeClass but the annotated method is executed after all test methods in the class have run. This can be used for final cleanup tasks or releasing resources that were set up in the @BeforeClass method.

In summary, @Before is executed before each test method, @BeforeClass is executed once before any test methods, @After is executed after each test method, and @AfterClass is executed once after all test methods are run.