Questions and answers for exam Preparation

MCQs

Total Questions : 10

What is the output of this program?

import java.util.*;
class Collection_iterators {
public static void main(String args[]) {
LinkedList list = new LinkedList();
list.add(new Integer(2));
list.add(new Integer(8));
list.add(new Integer(5));
list.add(new Integer(1));
Iterator i = list.iterator();
Collections.reverse(list);
Collections.shuffle(list);
i.next();
i.remove();
while(i.hasNext())
System.out.print(i.next() + " ");
}
}

2 8 5
2 1 8
2 5 8
8 5 1

Discuss Question

Answer: Option B. -> 2 1 8

i.next() returns the next element in the iteration. i.remove() removes from the underlying

collection the last element returned by this iterator (optional operation). This method can

be called only once per call to next(). The behavior of an iterator is unspecified if the

underlying collection is modified while the iteration is in progress in any way other than

by calling this method.
Output:
$ javac Collection_iterators.java
$ java Collection_iterators
2 1 8
(output will be different on your system)

Question 2.

What is the output of this program?

import java.util.*;
class Collection_iterators {
public static void main(String args[]) {
LinkedList list = new LinkedList();
list.add(new Integer(2));
list.add(new Integer(8));
list.add(new Integer(5));
list.add(new Integer(1));
Iterator i = list.iterator();
Collections.reverse(list);
Collections.sort(list);
while(i.hasNext())
System.out.print(i.next() + " ");
}
}

2 8 5 1
1 5 8 2
1 2 5 8
2 1 8 5

Discuss Question

Answer: Option C. -> 1 2 5 8

Collections.sort(list) sorts the given list, the list was 2->8->5->1 after sorting it

Question 3.

What is the output of this program?

import java.util.*;
class Collection_iterators {
public static void main(String args[]) {
LinkedList list = new LinkedList();
list.add(new Integer(2));
list.add(new Integer(8));
list.add(new Integer(5));
list.add(new Integer(1));
Iterator i = list.iterator();
Collections.reverse(list);
while(i.hasNext())
System.out.print(i.next() + " ");
}
}

2 8 5 1
1 5 8 2
2
2 1 8 5

Discuss Question

Answer: Option B. -> 1 5 8 2

Collections.reverse(list) reverses the given list, the list was 2->8->5->1 after

Question 4.

What is the output of this program?

import java.util.*;
class Collection_iterators {
public static void main(String args[]) {
ListIterator a = list.listIterator();
if(a.previousIndex()! = -1)
while(a.hasNext())
System.out.print(a.next() + " ");
else
System.out.print("EMPTY");
}
}