Question 1

What is the output of following piece of code ?

int x = 2;
 switch (x) {
 case 1:System.out.println("1?);
 case 2:
 case 3:System.out.println("3?);
 case 4:
 case 5:System.out.println("5?);
 }

java

No output
3 and 5
1, 3 and 5
3

Answer

Correct Option: B,D

Question 2

A method is defined in a class as : void processUser(int i) { } If this method is overriden in a sub class,_

java

the new method should return int
the new method can return any type of values
the argument list of new method should exactly match that of overriden method
the return type of new method should exactly match that of overriden method

AI Explanation

AI 1

To answer this question, we need to understand the concept of method overriding in Java.

Method overriding occurs when a subclass provides a specific implementation of a method that is already defined in its parent class. When overriding a method, certain rules must be followed. Let's go through each option to understand why it is correct or incorrect:

Option A) The new method should return int - This option is incorrect. The return type of the overriding method can be a subtype of the return type of the overridden method, but it cannot be a different type.

Option B) The new method can return any type of values - This option is incorrect. The return type of the overriding method should be covariant with the return type of the overridden method. In other words, it should be the same type or a subtype of the return type of the overridden method.

Option C) The argument list of the new method should exactly match that of the overridden method - This option is correct. The argument list of the overriding method should be the same as the argument list of the overridden method. This ensures that the method signature remains the same.

Option D) The return type of the new method should exactly match that of the overridden method - This option is incorrect. As mentioned earlier, the return type of the overriding method can be a subtype of the return type of the overridden method, but it cannot be a different type.

The correct answer is C. The argument list of the new method should exactly match that of the overridden method. This ensures that the method signature remains the same.

Therefore, the correct answer is option C.

Answer

Correct Option: C

Question 3

A Vector is declared as follows. What happens if the code tried to add 6 th element to this Vector new vector(5,10)

java

The element will be successfully added
ArrayIndexOutOfBounds Exception
The Vector allocates space to accommodate up to 15 elements
none of these

Answer

Correct Option: A,C

Question 4

A class can be converted to a thread by implementing the interface ___.

java

Thread
Runnable
Both of these
none of these

Answer

Correct Option: B

Question 5

Given:

TreeSet map = new TreeSet();
 map.add("one");
 map.add("two");
 map.add("three");
 map.add("four"};
 map.add("one");
 Iterator it = map.iterator();
 while (it.hasNext() ) {
 System.out.print( it.next() + " " );
 }

java

Compilation fails
one two three four
four three two one
four one three two
one two three four one
one four three two one

AI Explanation

AI 1

To answer this question, let's analyze the given code step by step:

TreeSet map = new TreeSet();
map.add("one");
map.add("two");
map.add("three");
map.add("four");
map.add("one");
Iterator it = map.iterator();
while (it.hasNext()) {
    System.out.print(it.next() + " ");
}

In this code, a TreeSet named map is created. A TreeSet is a collection that stores elements in a sorted and unique order.

The following elements are added to the map:

"one"
"two"
"three"
"four"
"one" (Note that "one" is added again)

Next, an iterator named it is created using the iterator() method of the TreeSet. The iterator allows iterating over the elements in the TreeSet in a sequential manner.

The while loop is then used to iterate over the elements in the TreeSet using the iterator. The condition it.hasNext() checks if there are more elements to iterate over. If there are, the loop continues.

Inside the loop, it.next() is used to retrieve the next element from the TreeSet. This element is then printed using System.out.print().

Let's analyze the output of the code:

The elements in the TreeSet are stored in a sorted order.
Since "four" comes before "one" in alphabetical order, "four" is printed first.
Next, "one" is printed.
"three" comes before "two" in alphabetical order, so "three" is printed next.
Finally, "two" is printed.

Therefore, the output of the code is: "four one three two".

The correct answer is D. "four one three two".

Answer

Correct Option: D

Question 6

Which is true about a method-local inner class?

java

It must be marked final
It can be marked abstract
It can be marked public
It can be marked static

Answer

Correct Option: B

Question 7

Which is true about an anonymous inner class?

java

It can extend exactly one class and implement exactly one interface
It can extend exactly one class and can implement multiple interfaces
It can extend exactly one class or implement exactly one interface
It can implement multiple interfaces regardless of whether it also extends a class
It can implement multiple interfaces if it does not extend a class

Answer

Correct Option: C

Question 8

Which is true?

java

The java command can access classes from more than one package, from a single JAR file.
JAR files can be used with the java command but not with the javac command.
In order for JAR files to be used by java, they MUST be placed in the /jre/lib/ext sub-directory within the J2SE directory tree.
When a part of a directory tree that includes subdirectories with files is put into a JAR file, all of the files are saved in the JAR file, but the subdirectory structure is lost.

Answer

Correct Option: A

Question 9

Which of the following statement is true?

java

X extends Y is correct if and only if X is a class and Y is an interface
X extends Y is correct if and only if X is an interface and Y is a class
X extends Y is correct if X and Y are either both classes or both interfaces
X extends Y is correct for all combinations of X and Y being classes and/or interfaces.

Answer

Correct Option: C

Description: Java Programming Language Quiz - 4
Number of Questions: 9
Created by: Aliensbrain Bot
Tags: java

Java Programming Language Quiz - 4

AI Explanation

AI Explanation

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