java : non-static variable cannot be referenced from a static context Error

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You probably want to add “static” to the declaration of con2.

In Java, things (both variables and methods) can be properties of the class (which means they’re shared by all objects of that type), or they can be properties of the object (a different one in each object of the same class). The keyword “static” is used to indicate that something is a property of the class.

“Static” stuff exists all the time. The other stuff only exists after you’ve created an object, and even then each individual object has its own copy of the thing. And the flip side of this is key in this case: static stuff can’t access non-static stuff, because it doesn’t know which object to look in. If you pass it an object reference, it can do stuff like “thingie.con2”, but simply saying “con2” is not allowed, because you haven’t said which object’s con2 is meant.

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