New to Java

Some classes don't have constructors. I understand that all classes will inherit a default constructor, but some classes don't appear to be objects at all. Classes that have main methods in particular seem to be intended not to define objects but instead simply to instantiate other objects and to execute code...... I'm going through a tutorial that has a plethora of example classes that fit this description, but when I create new classes in Netbeans they always provide me with a costructor shell and never provide me with a main method - why is this? is there a name for the type of class I'm describing? And how do you add this type of class to an existing project in Netbeans? I know that I can add main methods and delete constructors from the classes that I create in Netbeans, that's not the point of my question.