MCQs
Total Questions : 10
Question 1.
import java.util.*;
public class genericstack {
Stack stk = new Stack ();
public void push(E obj) {
stk.push(obj);
}
public E pop() {
E obj = stk.pop();
return obj;
}
}
class Output {
public static void main(String args[]) {
genericstack gs = new genericstack();
gs.push(36);
System.out.println(gs.pop());
}
}
What is the output of this program?
import java.util.*;
public class genericstack {
Stack stk = new Stack ();
public void push(E obj) {
stk.push(obj);
}
public E pop() {
E obj = stk.pop();
return obj;
}
}
class Output {
public static void main(String args[]) {
genericstack gs = new genericstack();
gs.push(36);
System.out.println(gs.pop());
}
}
Answer: Option D. -> Compilation Error
genericstack's object gs is defined to contain a string parameter but we are sending
an integer parameter, which results in compilation error.
Output:
$ javac Output.javac
$ java Output
Hello
Answer: Option A. -> 1
None.
Output:
$ javac Output.javac
$ java Output
1
Answer: Option B. -> 7.0
None.
Output:
$ javac Output.javac
$ java Output
7.0
Answer: Option D. -> 6.0
None.
Output:
$ javac Output.javac
$ java Output
6.0
Answer: Option B. -> super
A lower bounded wildcard is expressed using the wildcard character ('?'), following
by the super keyword, followed by its lower bound: .
Answer: Option C. -> When designing your own collections class (say, a linked list), generics and parameterized types allow you to achieve type safety with just a single class definition as opposed to defining multiple classes.
None.
Answer: Option A. -> ?
In generic code, the question mark (?), called the wildcard, represents an unknown type.
Answer: Option A. -> List
None.
Answer: Option A. -> It is used in cases when type being operated upon is not known.
The wildcard can be used in a variety of situations: as the type of a parameter, field, or
local variable; sometimes as a return type (though it is better programming practice to
be more specific). The wildcard is never used as a type argument for a generic
method invocation, a generic class instance creation, or a supertype.
Answer: Option C. -> extends
None.
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