Java Reference
In-Depth Information
//int a = al.v1; /* A compile-time error */
//int b = al.v2; /* A compile-time error */
//int c = al.v3; /* A compile-time error */
int d = al.v4;
System.out.println("d = " + d);
//al.m1(); /* A compile-time error */
//al.m2(); /* A compile-time error */
//al.m3(); /* A compile-time error */
al.m4();
/* Modify the values of instance variables */
//al.v2 = 20; /* A compile-time error */
//al.v3 = 30; /* A compile-time error */
al.v4 = 40;
System.out.println("After modifying v4...");
//al.m2(); /* A compile-time error */
//al.m3(); /* A compile-time error */
al.m4();
}
}
d = 400
Inside m4():
v1 = 100, v2 = 200, v3 = 300, v4 = 400
After modifying v4...
Inside m4():
v1 = 100, v2 = 200, v3 = 300, v4 = 40
Note the
AccessLevelTest2
class in the
com.jdojo.cls.p1
package, which is different from the
com.jdojo.cls
package in which the
AccessLevel
class exists. The code for the
AccessLevelTest2
class is similar to the code for the
AccessLevelTest1
class, except for the fact that most of the statements have been commented. Note that you need to
use an
import
statement to import the
AccessLevel
class from the
com.jdojo.cls
package so you can use its simple
name inside the
main()
method. In the
AccessLevelTest1
class, it was not necessary to import the
AccessLevel
class because they are in the same package. The
AccessLevelTest2
class can access only the
public
members of
the
AccessLevel
class because it is in a different package than the
AccessLevel
class. This is the reason that the
uncommented statements access only the
public
instance variable
v4
and the
public
method
m4()
. Note that even if
only the
v4
instance variable is accessible, you are able to print the values of
v1
,
v2
, and
v3
as well, by accessing them
indirectly through the public method
m4()
.
Let's consider a trickier situation. See Listing 6-17.
Listing 6-17.
A Class with Package-level Access Having a Public Instance Variable
// AccessLevel2.java
package com.jdojo.cls;
class AccessLevel2 {
public static int v1 = 600;
}
