Protected Keyword in Java with Examples

Access modifiers in Java help to restrict the scope of a class, constructor, variable, method, or data member. There are four types of access modifiers available in java. The access of various modifiers can be seen in the following table below as follows: 

👁 Difference Between Access Modifiers

The protected keyword in Java refers to one of its access modifiers. The methods or data members declared as protected can be accessed from

• Within the same class.
• Subclasses of the same packages.
• Different classes of the same packages.
• Subclasses of different packages.

There are some certain important points to be remembered as follows: 

1. If one wishes to access a protected modifier outside a package, then inheritance is needed to be applied.
2. Protecting a constructor prevents the users from creating the instance of the class, outside the package.
3. During overriding, when a variable or method is protected, it can be overridden to other subclass using either a public or protected modifier only.
4. Outer class and interface cannot be protected.

Implementation: Here we will be creating two packages p1 and p2. Class A in p1 is made public, to access it in p2. The method displayed in class A is protected and class B is inherited from class A and this protected method is then accessed by creating an object of class B.

Example 1: Package p1 

 
Package p2 

Output:

GeeksforGeeks

Now let us try to analyze different conditions of access: 

1. Calling protected function without extending the parent class
2. Accessing a protected class
3. Accessing display function from the same package but different 
4. Accessing display function from a different package
5. Accessing a protected class by overriding to sub-class within the same package

A. Calling Protected Function Without Extending the Parent Class

Here we will create two packages p1 and p2. Class A in p1 is made public, to access it in p2. The method displayed in class A is protected. But the code will not be able to access the function "display" since the child class has not inherited its value from the main class and will throw an exception as shown. 

Example 1-A: Package p1 

Example 1-B: Package p2 

Output:

Exception in thread "main" 
java.lang.RuntimeException: 
Uncompilable source code - 
Erroneous sym type: p2.B.display
 at p2.B.main(B.java:16)

B: Accessing a Protected Class

Here we are trying to access a protected class A resulting in an error. 

Example A:

Example B: Package p2 

Output: This will throw an error

Exception in thread "main" 
java.lang.RuntimeException: 
Uncompilable source code - 
Erroneous sym type: p2.B.display
 at p2.B.main(B.java:16)

C: Accessing Display Function From the Same Package But Different Class

Implementation: In this example, we have access to access a protected function "display" from the same package but a different class 

Example A: Package p1 

Example B: class C 

Output:

GeeksforGeeks

D: Accessing Display Function From a Different Package

Here we have tried to access the protected function display from a different package by inheritance and extending the class. 

Example A: Package p1 

Example B: Package p2 

Output:

GeeksforGeeks

E: Accessing a Protected Class by Overriding to Sub-Class Within the Same Package

Here we have designed two classes A and C, where class C is the overridden one. 

Example A: class A 

Example B: class C 

Output:

Class C