Advanced Packages and Access Modifiers in Java: Example 3
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Table of Content:
Within Package and Sub Package (default method)
We are trying to access a default method Within Same Package but from sub package different class
Save file: ClassA.java
package pack1;
class ClassA{
void MethodOfClassA()
{
System.out.println("Method of ClassA");
}
}
Save file: ClassB.java
package pack1.subpack1;
import pack1.ClassA;
class ClassB{
public static void main(String args[])
{
ClassA object = new ClassA();
object.MethodOfClassA();
}
}
C:\Users\Hello World>E:
E:\>javac -d . ClassA.java
E:\>javac -d . ClassB.java
ClassB.java:3: error: ClassA is not public in pack1; cannot be accessed from outside package
import pack1.ClassA;
^
ClassB.java:9: error: cannot find symbol
ClassA object = new ClassA();
^
symbol: class ClassA
location: class ClassB
ClassB.java:9: error: cannot find symbol
ClassA object = new ClassA();
^
symbol: class ClassA
location: class ClassB
3 errors
Within Package and Sub Package (public method)
We are trying to access a public method Within Same Package but from sub package different class
Save file: ClassA.java
package pack1;
public class ClassA{ // must be public
public void MethodOfClassA()
{
System.out.println("Method of ClassA");
}
}
Save file: ClassB.java
package pack1.subpack1;
import pack1.ClassA;
class ClassB{
public static void main(String args[])
{
ClassA object = new ClassA();
object.MethodOfClassA();
}
}
C:\Users\Hello World>E: E:\>javac -d . ClassA.java E:\>javac -d . ClassB.java E:\>java pack1.subpack1.ClassB Method of ClassA
Within Package and Sub Package (protected method)
We are trying to access a protected method Within Same Package but from sub package different class
Save file: ClassA.java
package pack1;
class ClassA{
protected void MethodOfClassA()
{
System.out.println("Method of ClassA");
}
}
Save file: ClassB.java
package pack1.subpack1;
import pack1.ClassA;
class ClassB{
public static void main(String args[])
{
ClassA object = new ClassA();
object.MethodOfClassA();
}
}
C:\Users\Hello World>E:
E:\>javac -d . ClassA.java
E:\>javac -d . ClassB.java
ClassB.java:3: error: ClassA is not public in pack1; cannot be accessed from outside package
import pack1.ClassA;
^
ClassB.java:9: error: cannot find symbol
ClassA object = new ClassA();
^
symbol: class ClassA
location: class ClassB
ClassB.java:9: error: cannot find symbol
ClassA object = new ClassA();
^
symbol: class ClassA
location: class ClassB
3 errors
Within Package and Sub Package (private method)
We are trying to access a private method Within Same Package but from sub package different class
if we change the class from private to public also the program will not run, to rum the programMethodOfClassA
should be public
Save file: ClassA.java
package pack1;
public class ClassA{
private void MethodOfClassA()
{
System.out.println("Method of ClassA");
}
}
Save file: ClassB.java
package pack1.subpack1;
import pack1.ClassA;
class ClassB{
public static void main(String args[])
{
ClassA object = new ClassA();
object.MethodOfClassA();
}
}
E:\>javac -d . ClassA.java
E:\>javac -d . ClassB.java
ClassB.java:10: error: MethodOfClassA() has private access in ClassA
object.MethodOfClassA();
^
1 error
Within Package and Sub Package (private method)
We are trying to access a private method Within Same Package but from sub package different class
ClassA is not public in pack1; cannot be accessed from outside package
MethodOfClassA() has private access in ClassA. It should not be private, it should be public to run.
Save file: ClassA.java
package pack1;
class ClassA{
private void MethodOfClassA()
{
System.out.println("Method of ClassA");
}
}
Save file: ClassB.java
package pack1.subpack1;
import pack1.ClassA;
class ClassB{
public static void main(String args[])
{
ClassA object = new ClassA();
object.MethodOfClassA();
}
}
E:\>javac -d . ClassA.java
E:\>javac -d . ClassB.java
ClassB.java:3: error: ClassA is not public in pack1; cannot be accessed from outside package
import pack1.ClassA;
^
ClassB.java:9: error: cannot find symbol
ClassA object = new ClassA();
^
symbol: class ClassA
location: class ClassB
ClassB.java:9: error: cannot find symbol
ClassA object = new ClassA();
^
symbol: class ClassA
location: class ClassB
3 errors