Objects

All data in Java falls into one of two categories: primitive data and objects. There are only eight primitive data types. However, Java has many types of objects, and you can invent as many others as you need. Any data type you invent will be a type of object.

Much more will be said about objects in future chapters (since Java is a object oriented programming language). The following is all you need to know, for now:

• A primitive data value uses a small, fixed number of bytes.
• There are only eight primitive data types.
• A programmer can not create new primitive data types.

• An object is a big block of data. An object may use many bytes of memory.
• An object usually consists of many internal pieces.
• The data type of an object is called its class.
• Many classes are already defined in Java.
• A programmer can invent new classes to meet the particular needs of a program.

A (crude) analogy is that a primitive data value is like a nut or a bolt, but an object is like a whole machine. If you want to learn more about objects right away, it would not hurt to jump ahead to the Chapter On Objects and read a few pages.