Question

AFAIK, there are three common types of Asserts people use in Java viz.,

• http://docs.oracle.com/javase/1.4.2/docs/guide/lang/assert.html
• http://static.springsource.org/spring/docs/1.2.x/api/org/springframework/util/Assert.html
• http://junit.sourceforge.net/javadoc/org/junit/Assert.html

Can you tell me the correct usage for each of the paradigm?

Answer 1

Options 1 and 2 are runtime assertions. They are usually used to make sure that you are getting only values that you expect to get.

Option 1 is more common since it’s a Java language feature. If you type assert into your code in an IDE, it will highlight it because it is a Java keyword (not part of the Jakarta library).

Option 2 is Spring-specific; looking at the docs that you linked to, it says that following:

Mainly for internal use within the framework; consider Jakarta’s Commons Lang >= 2.0 for a more comprehensive suite of assertion utilities.

Option 3 is used almost exclusively for jUnit testing. They ensure that your tests are outputting the values that you expect your code to produce.

Most likely, you will use Option 1 in the code that you write. As the docs say, you probably will never use Option 2. You will only use Option 3 if you write jUnit tests.