Access Specifiers/modifiers in java

Access Specifier:

• To Explicitly mention the way how the data (variables and methods of a class) available to outside.
• Access specifier is something which mentions the way how the member of a class has to be available to anything outside the class.
• Access specifiers not not applicable to the local variables.(present inside method).
• Access specifiers are the keywords using which we can control the accessibility of the members of a class.
• There are 4 different ways in which we can control the accessibility of the members of a class
• Thus there are "4" access specifiers and they are,

1. public
2. private
3. protected
4. default (not a keyword) 

• if we not specify any keyword that will be considered as default 

Public:

• The access specifier "public" makes the member of a class available to any location outside of the class.
• Thus anything mentioned as public would be available to any location outside the class.
• Means if we have a class with public access specifier then we can use it in other packages also by importing the corresponding package.

1. package package1;
2. public Class A{ 
3. public void show(){
4. }
5. public static void main (String args[]) {
6. }
7. }

1. package package2;
2. import package1.*;
3. public Class B {
4. public static void main (String args[]) {
5. A a = new A();
6.  a.show();
7. }
8. }

Private:

• Private would not allow the member of class available to any location outside the class.
• private members would be available only within the same class.
• Private members of a class would not be available to anything outside the class under any condition.
• Private members of a class would also be not available to the sub class objects

1. package package1;
2. Class A{ 
3. private void show(){
4. }
5. public static void main (String args[]) {
6. A a= new A();
7. a.show();
8. }
9. }

Default:

• Any member of class mentioned without any access specifier then its considers that as default .
• Default will act as "public " within the same package and same path.
• The same default would act as private outside the package.
• Default members of any class would be available to anything within the same package and would not be available outside the package under any condition.

1. package package1;
2. Class A{ 
3. void show(){
4. }
5. public static void main (String args[]) {
6. A a= new A(); // works fine in same class
7. a.show();
8. }
9. }

1. package package1;
2. Class B{ 
3. public static void main (String args[]) {
4. A a= new A(); // works fine in same package
5. a.show();
6. }
7. }

1. package package2;
2. import package1.*;
3. Class B{ 
4. public static void main (String args[]) {
5. A a= new A(); // gives an error
6. a.show(); // gives an error
7. }
8. }

 

Protected:

• protected will act as public within the same package and acts as private outside the package.
• But protected will also act as public outside the package only with respect to sub class objects.

1. package package1;
2. public Class A{ 
3. protected void show() {
4. }
5. }

1. package package2;
2. import package1.*;
3. public Class B extends A { 
4. public static void main (String args[]) {
5. B b= new B();
6. b.show();
7. }
8. }

• Access specifiers are applicable to static inner class and member inner class.
• Access specifiers are not applicable to anonymous inner class and local inner class