Protected links in Java
I have three classes:
package pac;
public class A {
protected A a;
protected final int i = 10;
}
public class B extends A {
void foo() {
A a = new A();
int b = a.a.i; //compiles fine
}
}
package another.pac;
public class C extends A {
void foo() {
A a = new A();
int b = a.a.i; //Does not compile. a.a is inaccessible
}
}
Why can't we access the protected member from a package to another package, but from the same package we can? They are both subclasses of one, so acces should be allowed.
JLS 6.6.2.1 says:
If access is by an access expression to the field E.Id or a method call expression E.Id (...) or a method reference expression E :: Id, where E is the primary expression (§15.8), then access is allowed if and only if when type E is S or a subclass of S.
The class C
satisfies the requirement. What's wrong?
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There is no need to make a link every time. I think you misunderstood Inheritance ..
public class B extends A {
void foo() {
// A a = new A(); No need to instantiate it here as B extends A
int b = i; //No nedd to refer it through a.a.i
}
}
package another.pac;
public class C extends A {
void foo() {
C c=new C();
int d=c.i//this will work fine
// A a = new A(); same as above explanation
int b = i; //same as above and even a.i will not compile
}
}
Your protected variable will now be available here.
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Class A is different from the pac package;
and class C is different from another.pac package so it won't be able to access its member. If C is different from the pac package then it will be able to access the item
See the following post: In Java, the difference between standard, public, secure and private
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