可以这样理解：
“同一类中可见”------“相对于父类，在父类的{}作用域内，父类的对象可以访问全部的成员”；
“同一包中对子类可见”------“相对于父类，与父类在同一包A中，在包A里面的子类的{}作用域内，父类或者子类的对象访问父类成员的情况”；
“同一包中对非子类可见”------“相对于父类，与父类在同一包A中，在包A里面的非子类的{}作用域内，父类或者子类的对象访问父类的成员的情况”；
“不同包中对子类可见”-------“相对于父类(在包A中)，与父类不在同一包(比如包B)中，在包B里面的子类的{}作用域内，子类的对象，访问父类的成员的情况”；
“不再同一包中对非子类可见”------“相对于父类(在包A中)，与父类不在同一包(比如包B)中，在包B里面的非子类的{}作用域内，父类或者子类的对象，访问父类的成员的情况”；
下面一行一行的解释：
一、
理解：
“同一类中可见”------“相对于父类，在父类的{}作用域内，父类的对象可以访问全部的成员”；
示例：
ClassA.java
1: package com.test.pkg1;
2:
3:
4:
5: public class ClassA {6:
7: public int a;
8: protected int b;
9: int c;
10: private int d;
11:
12: public void fun1(){}13: protected void fun2(){}14: void fun3(){}15: private void fun4(){}16:
17:
18: public static void main(String[] args) {19:
20: ClassA classA = new ClassA();
21:
22: classA.a = 0;
23: classA.b = 0;
24: classA.c = 0;
25: classA.d = 0;
26:
27: classA.fun1();
28: classA.fun2();
29: classA.fun3();
30: classA.fun4();
31:
32: }
33:
34:
35: }
36:
编译无误！
二、
理解：
“同一包中对子类可见”------“相对于父类，与父类在同一包A中，在包A里面的子类的{}作用域内，父类或者子类的对象访问父类成员的情况”；
ClassA.java
1: package com.test.pkg1;
2:
3:
4:
5: public class ClassA {6:
7: public int a;
8: protected int b;
9: int c;
10: private int d;
11:
12: public void fun1(){}13: protected void fun2(){}14: void fun3(){}15: private void fun4(){}16:
17:
18: public static void main(String[] args) {19:
20: ClassA classA = new ClassA();
21:
22: classA.a = 0;
23: classA.b = 0;
24: classA.c = 0;
25: classA.d = 0;
26:
27: classA.fun1();
28: classA.fun2();
29: classA.fun3();
30: classA.fun4();
31:
32: }
33:
34:
35: }
36:
37: class ClassB extends ClassA{38:
39: public void fun5()
40: {41: ClassA classA = new ClassA();
42: ClassB classB = new ClassB();
43:
44: classA.a = 0;
45: classA.b = 0;
46: classA.c = 0;
47: classA.d = 0;
48:
49: classA.fun1();
50: classA.fun2();
51: classA.fun3();
52: classA.fun4();
53:
54: classB.a = 0;
55: classB.b = 0;
56: classB.c = 0;
57: classB.d = 0;
58:
59: classB.fun1();
60: classB.fun2();
61: classB.fun3();
62: classB.fun4();
63: }
64: }
下面是系统提示：
三、
理解：
“同一包中对非子类可见”------“相对于父类，与父类在同一包A中，在包A里面的非子类的{}作用域内，父类或者子类的对象访问父类的成员的情况”；
ClassA.java
1: package com.test.pkg1;
2:
3:
4:
5: public class ClassA {6:
7: public int a;
8: protected int b;
9: int c;
10: private int d;
11:
12: public void fun1(){}13: protected void fun2(){}14: void fun3(){}15: private void fun4(){}16:
17:
18: public static void main(String[] args) {19:
20: ClassA classA = new ClassA();
21:
22: classA.a = 0;
23: classA.b = 0;
24: classA.c = 0;
25: classA.d = 0;
26:
27: classA.fun1();
28: classA.fun2();
29: classA.fun3();
30: classA.fun4();
31:
32: }
33:
34:
35: }
36:
37: class ClassB extends ClassA{}38:
39: class ClassC{40:
41: public void fun5()
42: {43: ClassA classA = new ClassA();
44: ClassB classB = new ClassB();
45:
46: classA.a = 0;
47: classA.b = 0;
48: classA.c = 0;
49: classA.d = 0;
50:
51: classA.fun1();
52: classA.fun2();
53: classA.fun3();
54: classA.fun4();
55:
56: classB.a = 0;
57: classB.b = 0;
58: classB.c = 0;
59: classB.d = 0;
60:
61: classB.fun1();
62: classB.fun2();
63: classB.fun3();
64: classB.fun4();
65: }
66: }
下面是系统提示：
四、
理解：
“不同包中对子类可见”-------“相对于父类(在包A中)，与父类不在同一包(比如包B)中，在包B里面的子类的{}作用域内，子类的对象，访问父类的成员的情况”；
ClassA.java
1: package com.test.pkg1;
2:
3:
4:
5: public class ClassA {6:
7: public int a;
8: protected int b;
9: int c;
10: private int d;
11:
12: public void fun1(){}13: protected void fun2(){}14: void fun3(){}15: private void fun4(){}16:
17:
18: public static void main(String[] args) {19:
20: ClassA classA = new ClassA();
21:
22: classA.a = 0;
23: classA.b = 0;
24: classA.c = 0;
25: classA.d = 0;
26:
27: classA.fun1();
28: classA.fun2();
29: classA.fun3();
30: classA.fun4();
31:
32: }
33:
34:
35: }
36:
ClassB.java
1: package com.test.pkg2;
2:
3: import com.test.pkg1.ClassA;
4:
5:
6: class ClassB extends ClassA{7:
8: public void fun5()
9: {10: ClassA classA = new ClassA();
11: ClassB classB = new ClassB();
12:
13: classA.a = 0;
14: classA.b = 0;
15: classA.c = 0;
16: classA.d = 0;
17:
18: classA.fun1();
19: classA.fun2();
20: classA.fun3();
21: classA.fun4();
22:
23: classB.a = 0;
24: classB.b = 0;
25: classB.c = 0;
26: classB.d = 0;
27:
28: classB.fun1();
29: classB.fun2();
30: classB.fun3();
31: classB.fun4();
32: }
33: }
下面是系统提示：
只需看关于ClassB的对象的提示。
五、
理解：
“不再同一包中对非子类可见”------“相对于父类(在包A中)，与父类不在同一包(比如包B)中，在包B里面的非子类的{}作用域内，父类或者子类的对象，访问父类的成员的情况”；
ClassA.java
1: package com.test.pkg1;
2:
3:
4:
5: public class ClassA {6:
7: public int a;
8: protected int b;
9: int c;
10: private int d;
11:
12: public void fun1(){}13: protected void fun2(){}14: void fun3(){}15: private void fun4(){}16:
17:
18: public static void main(String[] args) {19:
20: ClassA classA = new ClassA();
21:
22: classA.a = 0;
23: classA.b = 0;
24: classA.c = 0;
25: classA.d = 0;
26:
27: classA.fun1();
28: classA.fun2();
29: classA.fun3();
30: classA.fun4();
31:
32: }
33:
34:
35: }
36:
ClassB.java
1: package com.test.pkg2;
2:
3: import com.test.pkg1.ClassA;
4:
5:
6: class ClassB extends ClassA{7:
8:
9: }
10:
11:
12: class ClassC{13:
14: public void fun5()
15: {16: ClassA classA = new ClassA();
17: ClassB classB = new ClassB();
18:
19: classA.a = 0;
20: classA.b = 0;
21: classA.c = 0;
22: classA.d = 0;
23:
24: classA.fun1();
25: classA.fun2();
26: classA.fun3();
27: classA.fun4();
28:
29: classB.a = 0;
30: classB.b = 0;
31: classB.c = 0;
32: classB.d = 0;
33:
34: classB.fun1();
35: classB.fun2();
36: classB.fun3();
37: classB.fun4();
38: }
39: }
系统提示：
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