library class in java


I was reading as below

All the library classes are organized in several packages. For a class to use such
library classes, it needs to import them using the import statement

Using packages provides access control to classes.

I would like to know what it means by library class. How library class is different from regular java class(with or without main statement).

How access control is provided by packages?

Please advise
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CPColinSenior Java ArchitectCommented:
There is no difference between a "library" class and a "regular" class. The text you quoted is just referring to classes that are part of a library.

Packages can provide access control in the case of protected or package-private methods and variables. Protected members can be accessed by anything that extends the current class or any other class in the same package. Package-private members can be accessed only by other classes in the same package.

By the way,

For a class to use such library classes, it needs to import them using the import statement.

This isn't exactly true. You don't have to import a class in order to use it; you can fully qualify a class name (such as java.util.Collection) and use it just fine, without importing it.

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