Assertions

[jose chiramal]

Why do we say these about assertions :

1. Don't use assertions to validate arguments to a public method.

2. Don't use assertions to validate command line arguements.

Any particular reason for these DON'TS.

[Pushkar Choudhary]

This article on Assertions might be useful to you.

[Rob Spoor]

In short, you cannot guarantee that assertions are turned on. Therefore all checks you think are being performed may be in fact checked. For example:

public void doSomething(String s)
{
    assert s != null && s.length() > 0;

    char c = s.charAt(0);
}

When assertions are all of a sudden turned off your validation fails and you will get a different exception, one you don't expect. Use your own checking mechanism instead:

public void doSomething(String s)
{
    if (s == null || s.length() == 0)
    {
        throw new IllegalArgumentException("string is null or empty");
    }
    char c = s.charAt(0);
}

[Campbell Ritchie]

You use the assertions to find the places where Exceptions (as Rob has shown you) are necessary.