选择题
1:Which statement about the garbage collection mechanism are true?
age collection require additional programe code in cases where multiple threads are running.
programmer can indicate that a reference through a local variable is no longer of interest.
programmer has a mechanism that explicity and immediately frees the memory used by Java objects.
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();
();
}
void Mystery(){
s=”constructor”;
}
void go(){
tln(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();
();
}
void Mystery(){
s=”constructor”;
}
void go(){
tln(s);
}
}
code compliles but throws an exception at runtime
code runs but nothing appears in the standard output
code runs and “constructor” in the standard output
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?
after line 5.
after line 6
after line 7(that is,as the method returns)
r in this method
5:
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?
s InnerOne{ public static double methoda() {return d1;} }
ic class InnerOne{ static double methoda() {return d1;} }
ate class InnerOne{ double methoda() {return d1;} }
ic 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
