Answers for S&P1 Test 1 held on 9^th Feb 05

Q1. Declare a variable (speedOfLight) to store the speed of light (in meters per second) with high precision; initialize it with the value 112000.45.[2]

Ans: double speedOfLight=112000.45;

Q2. Declare and initialize a variable with the identifier gg, datatype float, and initial value 2.55 using a single statement.[3]

Ans: float gg = 2.55;

Q3. You are to represent monetary amounts (i.e. floating-point values consisting of dollars, a decimal, and cents; e.g. 2.19) using whole number datatypes (not real-valued datatypes). How would you do this? [4]

Ans: I would have two ints: one for dollars and one for cents or 2.19 as 219 cents. I could then use the discrete datatypes int or long to represent any dollar amount.

Q4. Which of the following choices is correct, A, B or both: [5]

A. The range of a double datatype is greater than a float

B. The precision of a double datatype is greater than a float

Ans: Both are correct

Q5. Write a simple expression that typecasts a byte datatype with the identifier bib into a char datatype with the identifier cic. [6]

Ans: cic = (char) bib;

Q6. Write a one-line expression that tests whether a previously declared double variable with the identifier value does not equal 3.14.[5]

Ans: ( value != 3.14 )

Q7. Write a method with the following signature that returns the sum of both parameters: [7]

public double sum(int i, int j) {

// your code goes here

}

Ans: public double sum(int i, int j){

return i + j;

}

Q8. Write a method with the following signature that returns true if the parameter is equal to 3 or 4, otherwise false: [7]

public boolean ttt(int number) {

// you code goes here

}

Ans: public boolean ttt(int number){

return number= =3 || number= =4;

}

Q9. Write a method with the following signature using if-else statements.

public void registrar_menu(int i);

The method does the following:

Displays “Add a course” if the parameter equals 1

Displays “Drop a course” if the parameter equals 2

Displays “Withdraw” if the parameter equals 3

Displays “Error” if the parameter equals anything else. [13]

public void registrar_menu(int i){

// your code should go here

}

An answer:

public void registrar_menu(int i) {

if (i = = 1)

System.out.println(“Add a course”);

else if (i = = 2)

System.out.println(“Drop a course”);

else if (i = = 3)

System.out.println(“Withdraw”);

else

System.out.println(“Error”);

}

Q10. I have declared the following two methods with the indicated signatures within the same class. [8]

public long time_of_day();

public long time_of_day(double x);

Is this legal Java?

1. True
2. False

Ans: True

Q11. What is the name of the first method that is called (if it exists) when a class is executed in JDK? [3]

Ans: main

Q12. What is the output produced by the following fragment of program code: [5]

int number;

number = (1/2)*3;

System.out.println(" (1/2)*3 equals " + number);

Ans: (1/2)*3 equals 0 because 1 / 2 =0 for integers

Q13. Write a method with the signature:

public void mmm(int n)

with a for loop that will print out the numbers 1,4,7, 10 ... until the parameter value n is reached. The method should ensure that the parameter n value is 1 or greater than 1, otherwise informing the user of their error. [17]

public void mmm(int n){

// your code goes here

}

An ans:

public void mmm(int n){

if (n >= 1){

for (int i = 1; i <= n; i+=3)

System.out.println(i);

}

else

System.out.println("Enter parameter 1 or greater");

}

Q14. Show the exact output that would be produced when the following program is executed. (If you explain your reasoning, you might get more partial credit for an incorrect answer.) [15]

public class TestQuestion {

public static void main(String[] args) {

int x, y;

x = 1;

y = 10;

while (x < y) {

x = x + 3;

System.out.println("x = " + x);

} // end while

} // end main

} // end class TestQuestion

Ans: x = 4

x = 7

x = 10