Adapted from Guy Steele's 'Growing a Language'
- A piece of data is a set of bits (0s and 1s) stored somewhere in the computer with a specific meaning.
- An object (in an object-oriented language like Java) is a piece of data whose meaning is specified by the rules of the language. In Java, these rules use types to make clear which parts of an object may cite other objects.
- Objects may be grouped to form classes. Knowing the class (or the type) of an object tells you most of what you need to know of how that object can act.
- Objects may have fields or variables. Each field of an object holds a piece of data. The data it holds may change throughout the program.
- Each field must have a type, which tells you what data can legally be stored in that field. A field may contain another object as its data.
- A method is a named piece of code that is also part of an object. If you can name or cite an object, then you can call a method of that object; the method then does its thing.
- The Java language has objects and classes and variables and methods and types...
Core Programming Concepts
Examples from a variety of sources including Dan Shiffman
's excellent tutorials