Answer Posted / sohil chhabriya

The access to classes, constructors, methods and fields are
regulated using access modifiers i.e. a class can control
what information or data can be accessible by other classes.
To take advantage of encapsulation, you should minimize
access whenever possible.

Java provides a number of access modifiers to help you set
the level of access you want for classes as well as the
fields, methods and constructors in your classes. A member
has package or default accessibility when no accessibility
modifier is specified.

Access Modifiers

1. private
2. protected
3. default
4. public

public access modifier

Fields, methods and constructors declared public (least
restrictive) within a public class are visible to any class
in the Java program, whether these classes are in the same
package or in another package.

private access modifier

The private (most restrictive) fields or methods cannot be
used for classes and Interfaces. It also cannot be used for
fields and methods within an interface. Fields, methods or
constructors declared private are strictly controlled, which
means they cannot be accesses by anywhere outside the
enclosing class. A standard design strategy is to make all
fields private and provide public getter methods for them.

protected access modifier

The protected fields or methods cannot be used for classes
and Interfaces. It also cannot be used for fields and
methods within an interface. Fields, methods and
constructors declared protected in a superclass can be
accessed only by subclasses in other packages. Classes in
the same package can also access protected fields, methods
and constructors as well, even if they are not a subclass of
the protected member’s class.

default access modifier

Java provides a default specifier which is used when no
access modifier is present. Any class, field, method or
constructor that has no declared access modifier is
accessible only by classes in the same package. The default
modifier is not used for fields and methods within an interface.

Below is a program to demonstrate the use of public,
private, protected and default access modifiers while
accessing fields and methods. The output of each of these
java files depict the Java access specifiers.

The first class is SubclassInSamePackage.java which is
present in pckage1 package. This java file contains the Base
class and a subclass within the enclosing class that belongs
to the same class as shown below.

package pckage1;

class BaseClass {

public int x = 10;
private int y = 10;
protected int z = 10;
int a = 10; //Implicit Default Access Modifier
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
private int getY() {
return y;
}
private void setY(int y) {
this.y = y;
}
protected int getZ() {
return z;
}
protected void setZ(int z) {
this.z = z;
}
int getA() {
return a;
}
void setA(int a) {
this.a = a;
}
}

public class SubclassInSamePackage extends BaseClass {

public static void main(String args[]) {
BaseClass rr = new BaseClass();
rr.z = 0;
SubclassInSamePackage subClassObj = new
SubclassInSamePackage();
//Access Modifiers - Public
System.out.println("Value of x is : " + subClassObj.x);
subClassObj.setX(20);
System.out.println("Value of x is : " + subClassObj.x);
//Access Modifiers - Public
// If we remove the comments it would result in a
compilaton
// error as the fields and methods being accessed are
private
/* System.out.println("Value of y is : "+subClassObj.y);

subClassObj.setY(20);

System.out.println("Value of y is : "+subClassObj.y);*/
//Access Modifiers - Protected
System.out.println("Value of z is : " + subClassObj.z);
subClassObj.setZ(30);
System.out.println("Value of z is : " + subClassObj.z);
//Access Modifiers - Default
System.out.println("Value of x is : " + subClassObj.a);
subClassObj.setA(20);
System.out.println("Value of x is : " + subClassObj.a);
}
}

Output

Value of x is : 10
Value of x is : 20
Value of z is : 10
Value of z is : 30
Value of x is : 10
Value of x is : 20

The second class is SubClassInDifferentPackage.java which is
present in a different package then the first one. This java
class extends First class (SubclassInSamePackage.java).

import pckage1.*;

public class SubClassInDifferentPackage extends
SubclassInSamePackage {

public int getZZZ() {
return z;
}

public static void main(String args[]) {
SubClassInDifferentPackage subClassDiffObj = new
SubClassInDifferentPackage();
SubclassInSamePackage subClassObj = new
SubclassInSamePackage();
//Access specifiers - Public
System.out.println("Value of x is : " + subClassObj.x);
subClassObj.setX(30);
System.out.println("Value of x is : " + subClassObj.x);
//Access specifiers - Private
// if we remove the comments it would result in a
compilaton
// error as the fields and methods being accessed are
private
/* System.out.println("Value of y is : "+subClassObj.y);

subClassObj.setY(20);

System.out.println("Value of y is : "+subClassObj.y);*/
//Access specifiers - Protected
// If we remove the comments it would result in a
compilaton
// error as the fields and methods being accessed are
protected.
/* System.out.println("Value of z is : "+subClassObj.z);

subClassObj.setZ(30);

System.out.println("Value of z is : "+subClassObj.z);*/
System.out.println("Value of z is : " +
subClassDiffObj.getZZZ());
//Access Modifiers - Default
// If we remove the comments it would result in a
compilaton
// error as the fields and methods being accessed are
default.
/*

System.out.println("Value of a is : "+subClassObj.a);

subClassObj.setA(20);

System.out.println("Value of a is : "+subClassObj.a);*/
}
}

Output

Value of x is : 10
Value of x is : 30
Value of z is : 10

The third class is ClassInDifferentPackage.java which is
present in a different package then the first one.

import pckage1.*;

public class ClassInDifferentPackage {

public static void main(String args[]) {
SubclassInSamePackage subClassObj = new
SubclassInSamePackage();
//Access Modifiers - Public
System.out.println("Value of x is : " + subClassObj.x);
subClassObj.setX(30);
System.out.println("Value of x is : " + subClassObj.x);
//Access Modifiers - Private
// If we remove the comments it would result in a
compilaton
// error as the fields and methods being accessed are
private
/* System.out.println("Value of y is : "+subClassObj.y);

subClassObj.setY(20);

System.out.println("Value of y is : "+subClassObj.y);*/
//Access Modifiers - Protected
// If we remove the comments it would result in a
compilaton
// error as the fields and methods being accessed are
protected.
/* System.out.println("Value of z is : "+subClassObj.z);

subClassObj.setZ(30);

System.out.println("Value of z is : "+subClassObj.z);*/
//Access Modifiers - Default
// If we remove the comments it would result in a
compilaton
// error as the fields and methods being accessed are
default.
/* System.out.println("Value of a is : "+subClassObj.a);

subClassObj.setA(20);

System.out.println("Value of a is : "+subClassObj.a);*/
}
}

Output

Value of x is : 10
Value of x is : 30

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