OXUS 20 JAVA Programming Questions and Answers PART II

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PART I – Single and Multiple choices, True/False and Blanks:
1) Which of the following correctly initializes an array myArray to contain four
elements each with value 0?
Why default 0 for int[] myArray = new int[4];?

 int[] myArray = { 0, 0, 0, 0 };

In Java Language Specification the Default /
Initial Value for any Object (class variable,

 int[] myArray = new int[4];

instance variable, or array component) can be



 For type byte, short and int the default value

int[] myArray = new int[4];
for (int i = 0; i < myArray.length; i++)
{

given as Follows:

is zero.
 For type long, the default value is zero, that
is, 0L.
 For type float, the default value is positive

myArray[i] = 0;

zero, that is, 0.0f.
 For type double, the default value is positive

}

zero, that is, 0.0d.

 All of the above

 For type char, the default value is the null
character, that is, 'u0000'.
 For type boolean, the default value is false.
 For all reference types, the default value is
null.

2) What will be the result of compiling following code?
public class MainTest {
public static void main(String args[]) {
System.out.println("OXUS 20");
}

The Java programming language
supports overloading methods, and Java can
distinguish between methods with
different method signatures.

public static void main(char args[]) {
System.out.println("Tricky!");
}
}

Two of the components of a method declaration
comprise the method signature — the method's
name and the parameter types.

 Code will not compile and will give "Duplicate main () method declaration" error
 Code will compile correctly but will give a runtime exception
 Code will compile correctly and will print "OXUS 20" (Without quotes) when it is run
 Code will compile correctly and will print "Tricky!" (Without quotes) when it is run

Abdul Rahman Sherzad

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3) What is y displayed in the following code?

 y is 3 -

public class Test {
public static void main(String[] args) {

Because of followings rules and

procedures:

int x = 1;

int y = x++

+

1

int y = x++ + x;

x;

2

x is initially 1, and x++ is still 1 because

System.out.println("y is " + y);
}

it is post increment; thus x will be 2
afterwards!

}

 y is 1

 y is 2

 y is 3

 y is 4

4) Assume int[] scores = {65, 75, 70, 90, 85}; which of the following statement
displays all the element values in the array?
There are a multiple ways to
print arrays in Java.

 System.out.println(scores);
 System.out.println(scores.toString());

One way is Using the static
method Arrays.toString(array)

 System.out.println(java.util.Arrays.toString(scores));

to get a string representation

 System.out.println(scores[0]);

of one dimensional arrays.

5) In Arrays, variables of type ................... can be used as an array indexes.

 short, long, String
 short, byte, char
 long, boolean, byte

The Java specification limits arrays to at most
Integer.MAX_VALUE elements. While a List may contain more
elements!


// Invalid

long[] primes_2 = new long[Long.MAX_VALUE];

 int, long, short

Long[] primes_1 = new Long[Long.MAX_VALUE];

// Invalid

long[] primes_3 = new long[Integer.MAX_VALUE]; // Valid

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6) Is 1.003 - 0.003 == 1.0?

 There is no guarantee that 1.003 - 0.003 == 1.0 is true.
 true
When comparing floating-point numbers (float, double) in Java, we quickly
discover that we get round-off errors. This has to do with the limited
precision of Java floating point variables. The following code example shows
the problem at hand:

 false

double num1 = 1.003;
System.out.println( num1 - num2 ); 1.003 – 0.003 = 0.9999999999999999
}
BUT
System.out.println( num1 - num2 ); 1.004 – 0.004 = 1.0
}

Comparing floating points:
•

You should rarely use the equality operator (==) when comparing two floating
point values (float or double)

•

Two floating point values are equal only if their underlying binary
representations match exactly

•

In many situations, you might consider two floating point numbers to be "close
enough" even if they aren't exactly equal

To determine the equality of two doubles or floats, use the following technique:
double a = 1.003;
double b = 0.003;
double c = a - b;
if (Math.abs(c - 1.0) <= 0.000001) {
System.out.println("Equal"); Equal
} else {
System.out.println("Not Equal");
}
}


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7) Programming style is important, because ______________.

 A program may not compile if it has a bad style
Good style is about making your
program clear and understandable
as well as easily modifiable.

 Good programming style can make a program run faster
 Good programming style makes a program more readable
 Good programming style helps reduce programming errors

8) What is the output of the following code?
public class Test {
int x = 0;

 x is 4

while (x < 4) {

- Because when x reach
at 4 the while condition
becomes false.

x = x + 1;
}

Note that the print statement
is outside of the while loop!

System.out.println("x is " + x);
}
}

 x is 1

 x is 2

 x is 3

 x is 4

9) Analyze the following code:
public class Test {
boolean even = false;
if (even = true) {

Please note assignment operator (=)
used instead of equality (==) the
following portion of the code:

if (even = true)

System.out.println("It is even!");
}
}

We assign true to the variable even,
and thus, even variable is always
true. Therefore, the statement "It is
even!" will be printed out.

}

 The program has a compile error.
 The program has a runtime error.
 The program runs, but displays nothing.
 The program runs and displays "It is even!" (Without quotes).


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10) What is the printout after the following loop terminates?
public class Test {
int number = 25;
int counter;
boolean isPrime = true;

for (counter = 2; counter < number && isPrime; counter++) {
if (number % counter == 0) {
isPrime = false;
}
}
System.out.println("counter is " + counter + " isPrime is " + isPrime);
}
}

 counter is 5 isPrime is true
 counter is 5 isPrime is false
 counter is 6 isPrime is true
 counter is 6 isPrime is false

Consider the following segment of the code:
if (number % counter == 0) {
isPrime = false;
}
When counter has the value of 5 the above condition evaluated
to true since 25 % 5 equals 0. Please note that we are inside
the loop and at the end the counter++ will be executed and
then the condition of the loop will be evaluated to false and
the loop will be terminated while counter has the value of 6.

11) .............

Which of the following is an example of a primitive data type?

 Integer

It's a coding convention, adopted by most Java programs

 String

that first letter of a Java classes be Capital. Therefore,

 Scanner

considering the conventions and standards all the options

 Random

are non-primitive!


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12) Is the following loop correct?
public class YouBetterTest {
for (;

; );

}
}

 Yes
 No

Above for loop is the same as following program:

for (;

; ) {

}
A for loop in java has the following structure:-

for (initialization statement; condition check; increment)
loop body;
As you can see, there are four statements in the for loop structure as follow: Initialization statement: This statement is executed only once, when the loop
is entered for the first time. This is an optional statement, meaning you can
choose keep this field blank.
 Conditional check: This statement is probably the most important one. It checks
to verify whether or not certain expression evaluates to true. If it is, then
the loop execution continues. You can choose to keep this field empty, which
will be evaluated to true.
 Increment / Decrement: This statement is used to increment / decrement some
variable.
 Loop body: The body of the loop, which will be executed again and again based
on the conditional check's truth value.

All in all, Now about the for (; ; ); syntax. It has no initialization
statement, so nothing will be executed. Its conditional check statement is also
empty, so which means it evaluates to true. After that the loop body is
executed. Next, since the incremental statement is empty, nothing is executed.
Then the conditional check is performed again which will again evaluates to true
and then this whole process will again repeat.


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is a
nonprofit society with the
aim of changing education for
the better by providing
education and assistance to
Computer Science and IT
professionals.

The

society's

goal

is

to

provide

information

and

assistance

to

Computer

Science

professionals, increase their job performance and overall agency function by providing
cost effective products, services and educational opportunities. So the society believes
with the education of Computer Science and IT they can help their nation to higher
standards of living.

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OXUS 20 JAVA Programming Questions and Answers PART II

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OXUS 20 JAVA Programming Questions and Answers PART II