Tutorial 4 - Answers

 

1.Indicate the output that will be produced.

int x=5, y=10, z;

z = x++ * ++y;

System.out.println (x + " " + y + " " + z);

 

Trace:

Steps

x

y

z

x=5;

5

 

 

y=10;

5

10

 

z;

5

10

 

z=x++ * ++y; Break Down

 

 

 

++y(do before evaluate)

5

(1+y)

11

 

            x++ (do after evaluation)

5

11

 

            x++ * ++y

5

11

55

            x++ (now can add 1 to x)

(x+1)

6

11

55

 

OUTPUT: 6 11 55

 

 

 

2.Indicate the values stored in a and b AFTER the statement is executed.  Assume that these statements are all executed on the same data:

 int a = 3, b = 9;

The first two are done for you:

 

Operation

a=3

b=9

Operation

a=3

b=9

++a;

(a=1+a)

4

9

b /= a;

(b=b/a)

3

3

a +=  b;

(a = a + b)

12

9

b %= 2;

(b=b%2)

3

1

++b;

(b=1+b)

3

10

a *= (b--);

(a=a*b)

(b=b-1) (after assignment)

27

8

a += ++b;

(a=a+ (1+b))

13

10

a += b++;

(a=a+b)

(b=b+1)

12

10

 

3.Trace the following program and write the screen dialogue when this program is executed.  Assume the input values are 4 and 5 respectively.

 

import java.io.*;

public class Mystery

{

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

     {

               int x, y;

               String inputString = ""; //read in string from screen

               InputStreamReader reader = new InputStreamReader(System.in);

               BufferedReader input = new BufferedReader(reader);

 

               System.out.println("What's up Doc?");

               System.out.println("\nEnter the first integer: ");

               inputString = input.readLine();

               x = new Integer(inputString).intValue();

               System.out.println("\nEnter the second integer: ");

               inputString = input.readLine();

               y = new Integer(inputString).intValue();

 

               if (x /2 ==0)

                  x = x*5;

               else

                  x = x/2;

               if (y/2 == 1)

                  y = y*5;

               else

                  y = y/2;

 

               x = x+y;

               y = y+x;

               System.out.println("\nThe mystery number is: " + y);

     }//end main

}//end class

 

 

 

 

 

 

 

 

 

                                                     Variables

                                             x                            y

 

                                             4                           

 

 

 

 

                                                                           5

 

(4/2=2) ==0 FALSE do ELSE

 

x=x/2                                   2

 

(y/2=2)==1 FALSE do ELSE

y=y/2                                                                 2

 

 

 

x=x+y(2+2)                        4

y=y+x(2+4)                                                   6                                             

           

Output:

 

What's up Doc?

 

Enter the first integer:

4

 

Enter the second integer:

5

 

The mystery number is: 6

 

 

4.For exercises 1 to 3, indicate the output that will be produced.  Assume the following declarations:

final int MAX=25, LIMIT=100;

int num1 = 12, num2 = 25, num3 = 87;

 

Exercises

Output

Exercise 2

if (num2 > 18)

            if (num1 < 0)

                System.out.println("apple");

            else

                System.out.println("orange");

System.out.println("pear");

 

25>18   TRUE do IF

            12<0 FALSE do else

 

 

            print orange

print pear

Exercise 2

if (LIMIT >= 4*num2)

            if (MAX == 25)

               System.out.println("apple");

            else

               System.out.println("orange");

else

            System.out.println("pear");

 

100>=100 TRUE do IF

            25==25 TRUE do IF

                        print apple

 

Exercise 3

if (num3 >= MAX)

{

            if (MAX/num2 = = 1)

                System.out.println("apple");

            System.out.println("orange");

            if (LIMIT-num3 > num1+2)

                System.out.println("pear");

            else

            {

                System.out.println("banana");

                System.out.println("kiwi");

            }

}

else

            if (num2*2 = = Max*2)

                System.out.println("grapefruit");

            else

                System.out.println("lime");

System.out.println("coconut");

 

87>=25  TRUE do IF

 

            (25/25=1)==1 TRUE do IF

                        print apple

            print orange

            (100-87=13)>14 FALSE do ELSE

 

 

 

                        print banana

                        print kiwi

 

 

 

 

 

 

 

print coconut

 

 

5.Write an application that asks the user to enter an integer (num) and then prints "num is zero", "num is even" or "num is odd" as appropriate based on the entered value of num.

 

For example, if the user entered in 7, then "The number entered is odd" would be printed to the screen.

 

/* Tutorial 4 - CSCI 1100/1202 Answers

   This program reads in an int and tells if it is zero, even or odd

*/

 

import java.io.*;

 

public class NumberValue

{

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

  {

     InputStreamReader reader = new InputStreamReader (System.in);

     BufferedReader input = new BufferedReader(reader);

     String text = ""; //to read in the line of text

     int value; //capture value entered by user

 

     //read in information

     System.out.print("Enter an integer: ");

     text = input.readLine();

     value = new Integer(text).intValue();

 

     //check to see if value is zero, even or odd (use the modulus operator)

 

    if (value == 0)

       System.out.println("The number entered is zero.");

    else

       if (value%2==0) //the value is even

         System.out.println("The number entered is even");

       else //the number is odd

         System.out.println("The number entered is odd");

 

   }//end main

}//end class