In Item 2 of the &quot;Effective Java, 2nd edition&quot; book, there is this snippet of code, in which the author wants to forbid the empty initialization of an object.

    class Example {
        private Example() {
            throw new AssertionError();
        }
    }

The type of exception thrown, is what confuses me here.

I don&#39;t understand if the `AssertionError` is thrown just because of an absence of more suited errors or because it should be this way.

As I understand, this error is thrown by the framework when an `assert` statement fails. Also, in the javadoc it&#39;s just written

&gt; [An AssertionError is] Thrown to indicate that an assertion has failed.

But I don&#39;t see any assertion (true-false statement) being violated here.
Of course the &quot;You shall not instantiate an item of this class&quot; statement has been violated, but if this is the logic behind that, then we should all throw `AssertionError`s everywhere, and that is obviously not what happens.

FWIW, I&#39;d have just thrown a

    new IllegalStateException(&quot;Must not instantiate an element of this class&quot;)

Is there something wrong with that? In which case should I throw an `AssertionError` in my own code?

Sorry if it&#39;s just a subtle doubt but I use this pattern a lot in my code and I want to make sure I&#39;m doing the right thing.

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What is an AssertionError? In which case should I throw it from my own code?