How to clean up null exception handling

Each developer has a different way of handling exceptions, but if that way looks messy, Why don't we use the assert?

    assert someobject != null;

If you do this, when some object is null, an error is caused by the alert statement

But usually, if some object is not supposed to be null, for some processing,

    if( someobject == null ){
            //someobject processing
    }
    someobject.somemethod();

I think it would be good to do it like this