Java Programming Questions and Answers

Showing 1 - 10 of 10 questions

Consider the following code fragment:

Integer w1 = new Integer(2);

Integer w2 = new Integer(2);

if(w1 == w2)

{

System.out.println("w1 is equal to w2!");

}

else

{

System.out.println("w1 is not equal to w2!");

}

What is the output of this code?

A. Compiler error

B. Runtime error

C. w1 is equal to w2!

D. w1 is not equal to w2!

correct answer d

Consider the following code fragment:

1. ArrayList list = new ArrayList();

2. list.add(new ObjectOne());

3. list.add(new ObjectOne());

4. list.add(new ObjectOne());

5. Collections.sort(list);

6. class ObjectOne {

7. private int x = 0;

8. private int y = 0;

9. }

What is the output of this code fragment?

A. Compiler error at line 5

B. Runtime error at line 5

C. Compiler error at line 3

D. Runtime error at line 3

correct answer a

Which of the following is an illegal line of code?

A. HashMap hmap = new HashMap();

B. ArrayList list = new ArrayList();

C. List list2 = new ArrayList ();

D. All of the above

correct answer b

Which of the following collections can you use to store key-value pairs and is thread safe?

A. HashTable

B. HashMap

C. TreeMap

D. Vector

correct answer a

Consider the following code fragment:

1. import java.io.*;

2. class MyClass{

3. public static void main(String[] args) throws IOException {

4. NumberStore ns = new NumberStore();

5. System.out.println("The number: " + ns.getInteger());

6. ns.setInteger(10);

7. System.out.println("The number: " + ns.getInteger());

8. }

9. }

10. class NumberStore {

11. int i =5;

12. public void setInteger(Integer x){

13. System.out.println("The number passed in is: " + x);

14. i = x;

15. }

16. public int getInteger( ){

17. return i;

18. }

19.}

What is the output?

A. Compiler error at line 6

B. Execution error at line 13

C. Compiler error at line 3

D. The number:5

The number passed in is:10

The number: 10

correct answer d

Consider the following code fragment:

1. ArrayList list = new ArrayList();

2. list.add(new Integer(1));

3. list.add(new Integer(2));

4. list.add(new Integer(3));

5. Iterator itr = list.iterator();

6. for(Integer wij:list){

7. System.out.println("number: " + wij);

8. }

What is the output from this code fragment?

A. number: 1

number: 2

number: 3

B. Compiler error at line 5

C. Compiler error at line 6

D. Runtime error

correct answer a

Which of the following statements is false?

A. A set is a collection that does not allow duplicates.

B. A map can store duplicate values.

C. A list is a collection that is ordered by index.

D. A list is a collection that cannot have duplicates.

correct answer d

Which of the following statements is not true about the hashcode?

A. The hashcode values of two equal objects must be equal.

B. The hashcode values of two unequal objects must be unequal.

C. If the hashcode values of two unequal objects are always unequal, it improves the performance.

D. A function that always returns a constant is not a very efficient function.

correct answer b

Consider the following code fragment:

1. int i = 5;

2. printIt(i);

3. void printIt(Integer wi) {

4. int j = wi;

5. System.out.println("The value is: " + j);

6. }

What is the output of this code?

A. The value is: 5

B. Compiler error at line 3

C. Compiler error at line 2

D. Runtime error

correct answer a

Which of the following classes implements the java.util.List interface?

A. Java.util.HashMapTable

B. Java.util.LinkedList

C. Java.util.HashTable

D. Java.util.OrderedList

correct answer b