java高级工程师笔试题

选择题

1:which is the main() method return of a application?

a.string

b.byte

c.char

d.void

2:

what will happen when you attempt to compile and run the following code?

int output = 10;

boolean b1 = false;

if((b1 true) && ((output += 10) 20))

{

system.out.println("we are equal " + output);

}

else

{

system.out.println("not equal! " + output);

}

choices:

what will happen when you attempt to compile and run the following code?

int output = 10;

boolean b1 = false;

if((b1 true) && ((output += 10) 20))

{

system.out.println("we are equal " + output);

}

else

{

system.out.println("not equal! " + output);

}

choices:

a.compilation error, attempting to perform binary comparison on logical data type

b.compilation and output of "we are equal 10".

c.compilation and output of "not equal! 20".

d.compilation and output of "not equal! 10".

3:

what will happen when you attempt to compile and run the following code?

class base

{

int i = 99;

public void amethod()

{

system.out.println("base.amethod()");

}

base()

{

amethod();

}

}

public class derived extends base

{

int i = -1;

public static void main(string argv[])

{

base b = new derived();

system.out.println(b.i);

b.amethod();

}

public void amethod()

{

system.out.println("derived.amethod()");

}

}

choices:

what will happen when you attempt to compile and run the following code?

class base

{

int i = 99;

public void amethod()

{

system.out.println("base.amethod()");

}

base()

{

amethod();

}

}

public class derived extends base

{

int i = -1;

public static void main(string argv[])

{

base b = new derived();

system.out.println(b.i);

b.amethod();

}

public void amethod()

{

system.out.println("derived.amethod()");

}

}

choices:

a.derived.amethod() -1 derived.amethod()

b.derived.amethod() 99

c.compile time error

d.derived.amethod()

4:

下述程序代码中有语法错误的行是( )。

int i,ia[10],ib[10]; /＊第一行＊/

for (i=0;i<=9;i++) /＊第2行＊/

ia[i]=0; /＊第3行＊/

ib=ia; /＊第4行＊/

下述程序代码中有语法错误的行是( )。

int i,ia[10],ib[10]; /＊第一行＊/

for (i=0;i<=9;i++) /＊第2行＊/

ia[i]=0; /＊第3行＊/

ib=ia; /＊第4行＊/

a.第1行

b.第2行

c.第3行

d.第4行

5:

what will be the result of executing the following code?

// filename; superclassx.java

package packagex;

public class superclassx

{

protected void superclassmethodx()

{

}

int superclassvarx;

}

// filename subclassy.java

1.package packagex.packagey;

2.

3.public class subclassy extends superclassx

4.{

5.superclassx objx = new subclassy();

6.subclassy objy = new subclassy();

7.void subclassmethody()

8.{

9.objy.superclassmethodx();

10.int i;

11.i = objy.superclassvarx;

12.}

13.}

choices:

what will be the result of executing the following code?

// filename; superclassx.java

package packagex;

public class superclassx

{

protected void superclassmethodx()

{

}

int superclassvarx;

}

// filename subclassy.java

1.package packagex.packagey;

2.

3.public class subclassy extends superclassx

4.{

5.superclassx objx = new subclassy();

6.subclassy objy = new subclassy();

7.void subclassmethody()

8.{

9.objy.superclassmethodx();

10.int i;

11.i = objy.superclassvarx;

12.}

13.}

choices:

a.compilation error at line 5

b.compilation error at line 9

c.runtime exception at line 11

d.none of these

6:which are not java keywords?

a.true

b.const

c.super

d.void

7: consider the class hierarchy shown below:

——————————————————————————————————

class fourwheeler implements drivingutilities

class car extends fourwheeler

class truck extends fourwheeler

class bus extends fourwheeler

class crane extends fourwheeler

———————————————————————————————————

consider the following code below:

1.drivingutilities du;

2.fourwheeler fw;

3.truck mytruck = new truck();

4.du = (drivingutilities)mytruck;

5.fw = new crane();

6.fw = du;

which of the statements below are true?

choices:

a.line 4 will not compile because an interface cannot refer to an object.

b.the code will compile and run.

c.the code will not compile without an explicit cast at line 6, because going down the hierarchy without casting is not allowed.

d.the code will compile if we put an explicit cast at line 6 but will throw an exception at runtime.

8:exhibit :

1. public class test (

2. private static int j = 0;

3.

4. private static boolean methodb(int k) (

5. j += k;

6. return true;

6. )

7.

8. public static void methoda(int i) {

9. boolean b:

10. b = i < 10 | methodb (4);

11. b = i < 10 || methodb (8);

12. )

13.

14. public static void main (string args[] } (

15. methoda (0);

16. system.out.printin(j);

17. )

18. )

what is the result?

a.the program prints “0”

b.the program prints “4”

c.the program prints “8”

d.the program prints “12”

9:

public class outerclass {

private double d1 = 1.0;

//insert code here

}

you need to insert an inner class declaration at line 3. which two inner class declarations are

valid?

public class outerclass {

private double d1 = 1.0;

//insert code here

}

you need to insert an inner class declaration at line 3. which two inner class declarations are

valid?

a.class innerone{ public static double methoda() {return d1;} }

b.public class innerone{ static double methoda() {return d1;} }

c.private class innerone{ double methoda() {return d1;} }

d.static class innerone{ protected double methoda() {return d1;} }

10:

the following code is entire contents of a file called example.java,causes precisely one error during compilation:

class subclass extends baseclass{

}

class baseclass(){

string str;

public baseclass(){

system.out.println(“ok”);}

public baseclass(string s){

str=s;}}

public class example{

public void method(){

subclass s=new subclass(“hello”);

baseclass b=new baseclass(“world”);

}

}

which line would be cause the error?

the following code is entire contents of a file called example.java,causes precisely one error during compilation:

class subclass extends baseclass{

}

class baseclass(){

string str;

public baseclass(){

system.out.println(“ok”);}

public baseclass(string s){

str=s;}}

public class example{

public void method(){

subclass s=new subclass(“hello”);

baseclass b=new baseclass(“world”);

}

}

which line would be cause the error?

a.9

b.10

c.11

d.12

11:

string s=”example string”;which operation is not legal?

string s=”example string”;which operation is not legal?

a.int i=s.length();

b.s[3]=”x”;

c.string short_s=s.trim();

d.string t=”root”+s;

12:软件生命周期的瀑布模型把软件项目分为3个阶段、8个子阶段，以下哪一个是正常的开发顺序?

a.计划阶段、开发阶段、运行阶段

b.设计阶段、开发阶段、编码阶段

c.设计阶段、编码阶段、维护阶段

d.计划阶段、编码阶段、测试阶段

13:which statements about java code security are not true?

a.the bytecode verifier loads all classes needed for the execution of a program.

b.executing code is performed by the runtime interpreter.

c.at runtime the bytecodes are loaded, checked and run in an interpreter.

d.the class loader adds security by separating the namespaces for the classes of the local file system from those imported from network sources.

14:a class design requires that a member variable should be accessible only by same package, which modifer word should be used?

a.protected

b.public

c.no modifer

d.private

15:

give the following method:

public void method( ){

string a,b;

a=new string(“hello world”);

b=new string(“game over”);

system.out.println(a+b+”ok”);

a=null;

a=b;

system.out.println(a);

}

in the absence of compiler optimization, which is the earliest point the object a refered is definitely elibile to be garbage collection.

give the following method:

public void method( ){

string a,b;

a=new string(“hello world”);

b=new string(“game over”);

system.out.println(a+b+”ok”);

a=null;

a=b;

system.out.println(a);

}

in the absence of compiler optimization, which is the earliest point the object a refered is definitely elibile to be garbage collection.

a.before line 5

b.before line 6

c.before line 7

d.before line 9

简答题

16:请阐述一下你对java多线程中“锁”的概念的理解。

17:列出jsp中包含外部文件的方式，两者有何区别。

18:请谈谈对一个系统设计的总体思路。针对这个思路，你觉得应该具备哪些方面的知识?

19:struts2中的拦截器，你用过那些自带的.拦截器，自己写过的吗?

20:怎样在复杂的各种形式的网页中提取mp3下载的结构化数据?

21:编写一个在二叉排序树中查找大小为第k的元素的算法。

22:java多线程编程。 用java写一个多线程程序，如写四个线程，二个加1，二个对一个变量减一，输出。

23:不允许使用系统时间，写出一个随机数生成函数。

24:hibernate中的id(主键)生成器有那些?或者你常用的是那些?

25:error和exception有什么区别?