Now let's look at ways we can modify classes, methods, and variables. There are two kinds of modifiers -- access modifiers and non-access modifiers. The access modifiers allow us to restrict access or provide more access to our code.
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Java Declaring classes, variables, and methods
Now let's look at ways we can modify classes, methods, and variables. There are two kinds of modifiers -- access modifiers and non-access modifiers. The access modifiers allow us to restrict access or provide more access to our code.
Class modifiers
The access modifiers available are public , private , and protected . However, a top-level class can have only public and default access levels. If no access modifier is specified, the class will have default access. Only classes within the same package can see a class with default access. When a class is declared as public, all the classes from other packages can access it.
Let's see the effect of some non-access modifiers on classes. The final keyword (see Java keywords and identifiers for more on keywords) does not allow the class to be extended. An abstract class cannot be instantiated, but can be extended by subclasses:
public final class Apple {..}
class GreenApple extends Apple {} // Not allowed, compile time error
Method and variable modifiers
All the access modifiers can be used for members of a class. The private members can only be accessed from inside the class. The protected members can only be accessed by classes in the same package or subclasses of the class. The public members can be accessed by any other class.
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