Access Modifiers

All methods will have an associated access that defines how and if the method can be called outside of the class in which it is defined. You can either specify the access explicitly with an access modifier or the method will be given default access if no access is specified. The four types of access a method can have are public , protected , private , and default.

• public ” no access restrictions. A public method can be called anywhere . This is the most commonly used access modifier for methods.

• protected ” can be called inside the class in which it is defined or inside a subclass of the class in which it is defined. Also available to any classes defined in the same package as the method.

• private ” can only be called inside the class in which it is defined. Intended for methods that are used internally inside a class.

• default ” if no access modifier is specified, a method has default access.

  The method has public access to other members inside the same package that the method is defined. The method is not accessible outside of the package in which it is defined.

The method access types and what they mean are summarized in Table 9.1. All methods are freely accessible inside the class in which they are defined. It is only outside of their class that access modifiers come into play.

Table 9.1. Method Accessibility

M ETHOD ACCESS TYPE	S AME CLASS	S AME PACKAGE	S UBCLASS , DIFFERENT PACKAGE	N ON-SUBCLASS , DIFFERENT PACKAGE
public	Yes	Yes	Yes	Yes
protected	Yes	Yes	Yes	No
private	Yes	No	No	No
default	Yes	Yes	No	No

Example: Method Access

The AccessDemo class defines two methods. The getTotalCost() method is meant to be accessed outside of the AccessDemo class and therefore is given public access. The secretMethod() method is intended for internal use only. To prevent outside access of this method, it is given private access.

 public class AccessDemo {   private double totalCost, fixedCost;   public AccessDemo(double fixed) {     fixedCost = fixed;   }   //  The getTotalCost() method is given public access.   //  The secretMethod() method is given private access.   public double getTotalCost() {     totalCost = fixedCost + secretMethod();     return totalCost;   }   private double secretMethod() {     return 1.4*fixedCost;   } } 

We next write a driver program for the AccessDemo class. The AccessDriver class creates an AccessDemo object. You can't call the secretMethod() method outside of the AccessDemo class. Any attempt to do so will result in a compiler error. The getTotalCost() method is public and can be called outside of the AccessDemo class.

 public class AccessDriver {   public static void main(String args[]) {     AccessDemo demo = new AccessDemo(1234.56);     //  Can't access the private method     //     demo.secretMethod();     //  Can access the public method     System.out.println("cost is " +                         demo.getTotalCost());   } } 

Output ”

 cost is 2962.944