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新华信国际信息咨询JAVA工程师笔试题
选择题
1:Which statement about the garbage collection mechanism are true?
A.Garbage collection require additional programe code in cases where multiple threads are running.
B.The programmer can indicate that a reference through a local variable is no longer of interest.
C.The programmer has a mechanism that explicity and immediately frees the memory used by Java objects.
D.The garbage collection mechanism can free the memory used by Java Object at explection time.
2:
Given:
1. public class test (
2. public static void main (String args[]) {
3. int i = 0xFFFFFFF1;
4. int j = ~i;
5.
6. }
7. )
What is the decimal value of j at line 5?
Given:
1. public class test (
2. public static void main (String args[]) {
3. int i = 0xFFFFFFF1;
4. int j = ~i;
5.
6. }
7. )
What is the decimal value of j at line 5?
A.0
B.1
C.14
D.-15
3:
What happens when you try to compile and run the following program?
class Mystery{
String s;
public static void main(String[] args){
Mystery m=new Mystery();
m.go();
}
void Mystery(){
s=”constructor”;
}
void go(){
System.out.println(s);
}
}
What happens when you try to compile and run the following program?
class Mystery{
String s;
public static void main(String[] args){
Mystery m=new Mystery();
m.go();
}
void Mystery(){
s=”constructor”;
}
void go(){
System.out.println(s);
}
}
A.this code compliles but throws an exception at runtime
B.this code runs but nothing appears in the standard output
C.this code runs and “constructor” in the standard output
D.this code runs and writes ”null” in the standard output
4:
public class X{
public Object m(){
Object o = new Float(3.14F);//line 3
Object [] oa = new Object[1];//line 4
oa[0] = o;//line 5
o=null;//line 6
return oa[0];//line 7
}
}
When is the Float object, created in line 3,eligible for garbage collection?
public class X{
public Object m(){
Object o = new Float(3.14F);//line 3
Object [] oa = new Object[1];//line 4
oa[0] = o;//line 5
o=null;//line 6
return oa[0];//line 7
}
}
When is the Float object, created in line 3,eligible for garbage collection?
A.just after line 5.
B.just after line 6
C.just after line 7(that is,as the method returns)
D.never in this method
5:
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
6:
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;} }
7:假定a和b为int型变量,则执行下述语句组后,b的值为
a=1;
b=10;
do
{
b-=a;
a++;
} while (b--<0);
A.9
B.-2
C.-1
D.8
8:
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;
9:
Give this class outline:
class Example{
private int x;
//rest of class body…
}
Assuming that x invoked by the code java Example, which statement can made x be directly accessible in main() method of Example.java?
Give this class outline:
class Example{
private int x;
//rest of class body…
}
Assuming that x invoked by the code java Example, which statement can made x be directly accessible in main() method of Example.java?
A.Change private int x to public int x
B.change private int x to static int x
C.Change private int x to protected int x
D.change private int x to final int x
10:
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()
11:
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
12:Which statement about listener is true?
A.Most component allow multiple listeners to be added.
B.If multiple listener be add to a single component, the event only affected one listener.
C.Component don?t allow multiple listeners to be add.
D.none
13:Which of the following answer is correct to express the value 8 in octal number?
A.010
B.0x10
C.08
D.0x8
14:
Give the following code:
public class Example{
public static void main(String args[] ){
int l=0;
do{
System.out.println(“Doing it for l is:”+l);
}while(--l>0)
System.out.println(“Finish”);
}
}
Which well be output:
Give the following code:
public class Example{
public static void main(String args[] ){
int l=0;
do{
System.out.println(“Doing it for l is:”+l);
}while(--l>0)
System.out.println(“Finish”);
}
}
Which well be output:
A.Doing it for l is 3
B.Doing it for l is 1
C.Doing it for l is 2
D.Doing it for l is 0
简答题
15:不用乘法或加法给一个数增加7倍。
16:abstract class和interface有什么区别?
17:用最有效率的方法算出2乘以8等於几?
18:说出在JSP页面里是怎么分页的?
19:四种会话跟踪技术。
20:调用系统命令实现删除文件的操作。
21:如果要设计一个图形系统，请你设计基本的图形元件(Point,Line,Rectangle,Triangle)的简单实现。
22:描述Cookie和Session的作用，区别和各自的应用范围，Session工作原理。
23:有A、B两个文件，文件格式相同，均为每行一个十进制整型数字，两个文件的行数不一定相等，但均在一千万行左右。A文件中的数字两两不等，B文件中的数字两两不等， 请用一个算法找出A和B两文件中所有相同的数，并且从小到大有序输出。请考虑统计程序如何实现，给出设计思路和关键算法(可使用伪代码)，并估计程序核心代码的时间复杂度和空间复杂度。
24:下面的代码有什么问题?
char *_strdup( const char *strSource )
{
static char str[MAX_STR_LEN];
strcpy(str, strSource);
return str;
}
25:Security 公司的网络管理工程师Mr. leak最近发现有不少来自公司外部IP的请求，试图非法访问公司内部资源，为了不影响数据访问流程。他不得不写一个高效的程序——一个工作在Ipv4上的防火墙，如果请求来自非授权的ip地址，则将请求丢弃。为了便于管理，通过文本文件IP.TXT来配置授权的IP地址，文件格式为每行(’/n’)一个 IP地址(或IP段)，范围不超过一个B类。例如：
162.105.91.163
59.66.105.0 59.66.105.255
211.71.0.0 211.71.255.255
限制：IP段的起止地址间以空格隔开。文件不超过10万行，内存不超过4M字节。
要求：请编写一个程序，读入IP.TXT文件。并从标准输入接受一个IP地址。如果该地址在授权范围内，则在标准输出上打印Y,否则打印N.如果输入为一个空行，程序结束。
请给出思路(文字描述)，完成代码，分析你采用算法的优劣。请列举测试方法和思路
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