java進階工程師筆試題
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:
下述程式代碼中有文法錯誤的行是( )。
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＊/
下述程式代碼中有文法錯誤的行是( )。
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:軟體生命周期的瀑布模型把軟體項目分為3個階段、8個子階段，以下哪一個是正常的開發順序?
a.計劃階段、開發階段、運作階段
b.設計階段、開發階段、編碼階段
c.設計階段、編碼階段、維護階段
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
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