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java高級工程師筆試題
選擇題
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:
下述程序代碼中有語法錯誤的行是( )。
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＊/
下述程序代碼中有語法錯誤的行是( )。
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:軟件生命周期的瀑布模型把軟件項目分為3個階段、8個子階段，以下哪一個是正常的開發(fā)順序?
a.計劃階段、開發(fā)階段、運行階段
b.設(shè)計階段、開發(fā)階段、編碼階段
c.設(shè)計階段、編碼階段、維護(hù)階段
d.計劃階段、編碼階段、測試階段
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
簡答題
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18:請談?wù)剬σ粋�系統(tǒng)設(shè)計的總體思路。針對這個思路，你覺得應(yīng)該具備哪些方面的知識?
19:struts2中的攔截器，你用過那些自帶的攔截器，自己寫過的嗎?
20:怎樣在復(fù)雜的各種形式的網(wǎng)頁中提取mp3下載的結(jié)構(gòu)化數(shù)據(jù)?
21:編寫一個在二叉排序樹中查找大小為第k的元素的算法。
22:java多線程編程。 用java寫一個多線程程序，如寫四個線程，二個加1，二個對一個變量減一，輸出。
23:不允許使用系統(tǒng)時間，寫出一個隨機數(shù)生成函數(shù)。
24:hibernate中的id(主鍵)生成器有那些?或者你常用的是那些?
25:error和exception有什么區(qū)別?
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