4.9. Multiple Choice Exercises

4.9.1. Easy Multiple Choice Questions

These problems are easier than most of those that you will usually see on the AP CS A exam.

    4-9-1: What does the following code print?

    for (int i = 3; i <= 12; i++)
    {
       System.out.print(i + " ");
    }
    
  • 5 6 7 8 9
  • What is i set to in the initialization area?
  • 4 5 6 7 8 9 10 11 12
  • What is i set to in the initialization area?
  • 3 5 7 9 11
  • This loop changes i by 1 each time in the change area.
  • 3 4 5 6 7 8 9 10 11 12
  • The value of i starts at 3 and this loop will execute until i equals 12. The last time through the loop the value of i is 12 at the begininng and then it will be incremented to 13 which stops the loop since 13 is not less than or equal to 12.

    4-9-2: How many times does the following method print a *?

    for (int i = 3; i < 9; i++)
    {
       System.out.print("*");
    }
    
  • 9
  • This would be true if i started at 0.
  • 7
  • Note that it stops when i is 9.
  • 6
  • Since i starts at 3 and the last time through the loop it is 8 the loop executes 8 - 3 + 1 times = 6 times.
  • 10
  • This would be true if i started at 0 and ended when i was 10. Does it?

    4-9-3: What does the following code print?

    int x = -5;
    while (x < 0)
    {
       x++;
       System.out.print(x + " ");
    }
    
  • 5 4 3 2 1
  • x is initialized (set) to -5 to start.
  • -5 -4 -3 -2 -1
  • x is incremented (x++) before the print statement executes.
  • -4 -3 -2 -1 0
  • x is set to -5 to start but then incremented by 1 so it first prints -4.

    4-9-4: How many times does the following method print a *?

    for (int i = 5; i <= 12; i++)
    {
       System.out.print("*");
    }
    
  • 7
  • This would be true if it stopped when i was 12, but it loops when i is 12.
  • 8
  • Note that it stops when i is 13 so 13 - 5 is 8.
  • 12
  • This would be true if i started at 1.
  • 13
  • This would be true if i started at 0.

    4-9-5: How many times does the following method print a *?

    for (int i = 1; i < 5; i++)
    {
       System.out.print("*");
    }
    
  • 4
  • The loop starts with i = 1 and loops as long as it is less than 5 so i is 1, 2, 3, 4.
  • 5
  • This would be true if the condition was i <= 5.
  • 6
  • This would be true if i started at 0 and ended when it reached 6 (i <= 5).

    4-9-6: How many times does the following method print a *?

    for (int i = 0; i <= 8; i++)
    {
       System.out.print("*");
    }
    
  • 7
  • This would be true if i started at 1 and ended when it reached 8.
  • 8
  • This would be true if the loop ended when i reached 8.
  • 9
  • This loop starts with i = 0 and continues till it reaches 9 so (9 - 0 = 9).

    4-9-7: How many times does the following method print a *?

    for (int x = 0; x < 5; x++)
    {
       System.out.print("*");
    }
    
  • 4
  • This would be true if x started at 1 instead of 0.
  • 5
  • The loop starts with x = 0 and ends when it reaches 5 so 5 - 0 = 5.
  • 6
  • This would be true if the condition was x <= 5 instead of x = 5.

    4-9-8: How many times does the following method print a *?

    for (int x = 2; x < 8; x++)
    {
       System.out.print("*");
    }
    
  • 6
  • This loop starts with x = 2 and continues while it is less than 8 so 8 - 2 = 6.
  • 7
  • This would be true if the loop ended when x was 9 instead of 8 (x <= 8).
  • 8
  • This would be true if the loop started with x = 0.

    4-9-9: What does the following code print?

    int x = 0;
    while (x <= 5)
    {
       System.out.print(x + " ");
       x++;
    }
    
  • 1 2 3 4
  • This would be true if x started at 1 and ended when x was 5.
  • 1 2 3 4 5
  • This would be true if x started at 1.
  • 0 1 2 3 4
  • This would be true if the loop ended when x was 5.
  • 0 1 2 3 4 5
  • This loop starts with x = 0 and ends when it reaches 6.

    4-9-10: What does the following code print?

    int x = 3;
    while (x < 9)
    {
       System.out.print(x + " ");
    }
    
  • 3 4 5 6 7 8
  • Notice that x isn't changed in the loop.
  • 3 4 5 6 7 8 9
  • Notice that x isn't changed in the loop.
  • 0 1 2 3 4 5 6 7 8
  • Notice that x isn't changed in the loop.
  • 0 1 2 3 4 5 6 7 8 9
  • Notice that x isn't changed in the loop.
  • It is an infinite loop
  • Since x is never changed in the loop this is an infinite loop.

4.9.2. Medium Multiple Choice Questions

These problems are similar to those you will see on the AP CS A exam.

    4-9-11: How many stars are output when the following code is executed?

    for (int i = 0; i < 5; i++) {
       for (int j = 0; j < 5; j++)
          System.out.println("*");
    }
    
  • 10
  • The second loop executes 5 times for each of the 5 times the first loop executes, so the answer should be 5 * 5.
  • 5
  • The second loop executes 5 times for each of the 5 times the first loop executes, so the answer should be 5 * 5.
  • 25
  • The first loop will execute 5 times, and for each time through, the second loop will execute 5 times. So the answer is the number of times through the first loop times the number of times through the second.
  • 50
  • The second loop executes 5 times for each of the 5 times the first loop executes, so the answer should be 5 * 5.
  • 15
  • The second loop executes 5 times for each of the 5 times the first loop executes, so the answer should be 5 * 5.

    4-9-12: Which of the following code segments will produce the displayed output?

    1
    22
    333
    4444
    55555
    
    
    I.   for (int i = 1; i <= 5; i++) {
            for (int j = i; j > 0; j--) {
               System.out.print(i);
            }
            System.out.println();
         }
    
    II.  for (int i = 0; i < 5; i++) {
            for (int j = 0; j < i; j++) {
               System.out.print(i);
            }
            System.out.println();
         }
    
    III. for (int i = 1; i < 5; i++) {
            for (int j = i; j > 0; j--) {
               System.out.print(i);
            }
            System.out.println();
         }
    
    IV.  for (int i = 1; i < 6; i++) {
            for (int j = 0; j < i; j++) {
               System.out.println(i);
            }
         }
    
    V.   for (int i = 0; i < 5; i++) {
            for (int j = 0; j < i; j++) {
               System.out.print(i+1);
            }
            System.out.println();
         }
    
  • I
  • This will loop with i changing from 1 to 5 and then for each i, j will loop from i to 0 printing the value of i and then a new line.
  • II
  • This will loop i from 0 to 4 and j from 0 to i, neglecting to ouput 5.
  • III
  • This will loop with i changing from 1 to 4 and j from i to 0.
  • IV
  • This will loop with i changing from 1 to 5 and j from 0 to i but it will print each value on a different line.
  • V
  • This will loop with i changing from 0 to 4 and j from 0 to i.

    4-9-13: What is printed as a result of the following code segment?

    for (int k = 0; k < 20; k+=2) {
       if (k % 3 == 1)
          System.out.print(k + " ");
    }
    
  • 0 2 4 6 8 10 12 14 16 18
  • This would be correct if we were printing out all of the values of k, not just the ones that have a remainder of 1 when divided by 3.
  • 4 16
  • This is missing the value 10 (10 divided by 3 does have a remainder of 1).
  • 0 6 12 18
  • None of these answers have a remainder of 1 when divided by 3.
  • 1 4 7 10 13 16 19
  • This answer would be correct if k was incremented by 1 instead of 2. K will be 0, 2, 4, 6, 8, 10, 12, 14, 16, 18 in this loop.
  • 4 10 16
  • This will loop with k having a value of 0 to 18 (it will stop when k = 20). It will print out the value of k followed by a space when the remainder of dividing k by 3 is 1.

    4-9-14: Which of the following code segments will produce the displayed output?

    11111
    2222
    333
    44
    5
    
    
    I.   for (int j = 1; j <= 5; j++) {
            for (int k = 5; k >= j; k--) {
               System.out.print(j + " ");
            }
            System.out.println();
         }
    
    II.  for (int j = 1; j <= 5; j++) {
            for (int k = 5; k >= 1; k--) {
               System.out.print(j + " ");
            }
            System.out.println();
         }
    
    III. for (int j = 1; j <= 5; j++) {
            for (int k = 1; k <= j; k++) {
               System.out.print(j + " ");
            }
            System.out.println();
         }
    
    IV.  for (int j = 1; j <= 5; j++) {
            for (int k = 1; k <= 5; k++) {
               System.out.println(j + " ");
            }
         }
    
    V.   for (int j = 1; j <= 5; j++) {
            for (int k = j; k <= 5; k++) {
               System.out.print(k + " ");
            }
            System.out.println();
         }
    
  • I
  • This will loop with j from 1 to 5 and k from 5 to j and print out the value of j and a space. So the first time through the loop it will print 1 five times and the next time it will print out 2 four times and so on.
  • II
  • This will print out each value from 1 to 5 five times.
  • III
  • This will loop with j from 1 to 5 and k from 1 times.
  • IV
  • This will loop j from 1 to 5 and k from 1 to 5, printing each number 5 times.
  • V
  • This loops with j from 1 to 5 and k from j to 5 and prints out the value of k, printing 1 through 5 on the first line, 2 through 5 on the next, and so on.

    4-9-15: What are the values of var1 and var2 after the following code segment is executed and the while loop finishes?

    int var1 = 0;
    int var2 = 2;
    
    while ((var2 != 0) && ((var1 / var2) >= 0)) {
       var1 = var1 + 1;
       var2 = var2 - 1;
    }
    
  • var1 = 0, var2 = 2
  • This would be true if the body of the while loop never executed. This would have happened if the while check was if var1 != 0 instead of var2 != 0
  • var1 = 1, var2 = 1
  • This would be true if the body of the while loop only execued one time, but it executes twice.
  • var1 = 3, var2 = -1
  • This would be true if the body of the while loop executed 3 times, but it executes twice.
  • var1 = 2, var2 = 0
  • The loop starts with var1=0 and var2=2. The while checks that var2 isn't 0 and that var1/var2 is greater than or equal to zero (0/2=0) so this is equal to zero and the body of the while loop will execute. The variable var1 has 1 added to it for a new value of 1. The variable var2 has 1 subtracted from it for a value of 1. At this point var1=1 and var2=1. The while condition is checked again. Since var2 isn't 0 and var1/var2 (1/1=1) is >=0 so the body of the loop will execute a second time. The variable var1 has 1 added to it for a new value of 2. The variable var2 has 1 subtracted from it for a value of 0. At this point var1=2 and var2=0. The while condition is checked again. Since var2 is zero the while loop stops and the value of var1 is 2 and var2 is 0.
  • The loop won't finish executing because of a division by zero.
  • 0/2 won't cause a division by zero. The result is just zero.
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