关于Java Access Control的4道有趣的测试题

好像很简单，测试一下，看你能答对几个？ （答案在最后）

 

问题1

public class p1.C1 { int m() {return 1;}}public class p1.C2 extends C1 { int m() {return 2;}}public class p2.C3 extends p1.C2 { int m() {return 3;}}public class p1.Main { public static void main(String[] args) { C1 c = new p2.C3(); System.out.println(c.m()); }}

Classes C1, C2 and Main are in package p1. C3 is in package p2. What is the output of Main.main()?

a)  1

b)  2

c)  3

问题2

public class p1.C1 { int m() {return 1;}}public class p1.C2 extends C1 { int m() {return 2;}}public class p2.C3 extends p1.C2 { public int m() {return 3;}}public class p1.Main { public static void main(String[] args) { C1 c = new p2.C3(); System.out.println(c.m()); }}

Classes C1, C2 and Main are in package p1. C3 is in package p2. What is the output of Main.main()?

a)  1

b)  2

c)  3

问题3:

public class p1.C1 { int m() {return 1;}}public class p1.C2 extends C1 { protected int m() {return 2;}}public class p2.C3 extends p1.C2 { protected int m() {return 3;}}public class p1.Main { public static void main(String[] args) { C1 c = new p2.C3(); System.out.println(c.m()); }}

Classes C1, C2 and Main are in package p1. C3 is in package p2. What is the output of Main.main()?

a)  1

b)  2

c)  3

问题4

public class p1.C1 { int m() {return 1;}}public class p1.C2 extends C1 { int m() {return 2;}}public class p2.C3 extends p1.C2 { int m() {return 3;}}public class p1.C4 extends p2.C3 { int m() {return 4;}}public class p1.Main { public static void main(String[] args) { C1 c = new p2.C4(); System.out.println(c.m()); }}

Classes C1, C2 and Main are in package p1. C3 is in package p2. What is the output of Main.main()?

a)  1

b)  2

c)  3

d)  4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

答案：

问题1: b

问题2: b

问题3: c

问题4: d