CSA unit 6 test review

Consider the following code segment.
int[] arr = {1, 2, 3, 4, 5};
Which of the following code segments would correctly set the first two elements of array arr to 10 so that the new value of array arr will be {10, 10, 3, 4, 5} ?

• arr[0] = 10;
  arr[1] = 10;

• arr[1] = 10;
  arr[2] = 10;

• arr[0, 1] = 10;

• arr[1, 2] = 10;

• arr = 10, 10, 3, 4, 5;

Consider the following method.
public int[] transform(int[] a)
{
a[0]++;
a[2]++;
return a;
}
The following code segment appears in a method in the same class as transform.
/ missing code /
arr = transform(arr);
After executing the code segment, the array arr should contain {1, 0, 1, 0}. Which of the following can be used to replace / missing code / so that the code segment works as intended?
int[] arr = {0, 0, 0, 0};
int[] arr = new int[0];
int[] arr = new int[4];

• I only

• II only

• III only

• I and II

• I and III

Consider the following method. Method allEven is intended to return true if all elements in array arr are even numbers; otherwise, it should return false.

public boolean allEven(int[] arr)

{

boolean isEven = /* expression */ ;

for (int k = 0; k < arr.length; k++)

{

/* loop body */

}

return isEven;

}

Which of the following replacements for /* expression / and / loop body */ should be used so that method allEven will work as intended?

• /* expression // loop body */

  false -----

  if ((arr[k] % 2) == 0)

  isEven = true;

• /* expression // loop body */

  false-----

  if ((arr[k] % 2) != 0)

  isEven = false;

  else

  isEven = true;

• /* expression // loop body */

  true-----

  if ((arr[k] % 2) != 0)

  isEven = false;

• /* expression // loop body */

  true-----

  if ((arr[k] % 2) != 0)

  isEven = false;

  else

  isEven = true;

• /* expression // loop body */

  true-----

  if ((arr[k] % 2) == 0)

  isEven = false;

  else

  isEven = true;

Consider the following instance variable and incomplete method. The method is intended to return a string from the array words that would be last alphabetically.

private String[] words;

public String findLastWord()

{

/* missing implementation */

}

Assume that words has been initialized with one or more strings containing only lowercase letters. Which of the following code segments can be used to replace /* missing implementation */ so that findLastWord will work as intended?

• int maxIndex = 0;

  for (int k = 0; k < words.length; k++)

  {

  if (words[k].compareTo(maxIndex) > 0)

  {

  maxIndex = k;

  }

  }

  return words[maxIndex];

• int maxIndex = 0;

  for (int k = 1; k <= words.length; k++)

  {

  if (words[k].compareTo(words[maxIndex]) > 0)

  {

  maxIndex = k;

  }

  }

  return words[maxIndex];

• int maxIndex = 0;

  for (int k = 1; k < words.length; k++)

  {

  if (words[k].compareTo(words[maxIndex]) > 0)

  {

  maxIndex = k;

  }

  }

  return maxIndex;

• String maxWord = words[0];

  for (int k = 1; k < words.length; k++)

  {

  if (words[k].compareTo(maxWord) > 0)

  {

  maxWord = k;

  }

  }

  return maxWord;

• String maxWord = words[0];

  for (int k = 1; k < words.length; k++)

  {

  if (words[k].compareTo(maxWord) > 0)

  {

  maxWord = words[k];

  }

  }

  return maxWord;

A BoundedintArray represents an indexed list of integers. In a BoundedIntArray the user can specify a size, in which case the indices range from 0 to size - 1. The user can also specify the lowest index, low, in which case the indices can range from low to low + size - 1.

public class BoundedIntArray

{

private int[] myItems; // storage for the list

private int myLowIndex; // lowest index

public BoundedIntArray(int size)

{

myItems = new int[size];

myLowIndex = 0;

}

public BoundedIntArray(int size, int low)

{

myItems = new int[size];

myLowIndex = low;

}

// other methods not shown

}

Consider the following statements.

BoundedIntArray arrl = new BoundedIntArray(100, 5);

BoundedIntArray arr2 = new BoundedIntArray(100);

Which of the following best describes arrl and arr2 after these statements?

• arrl and arr2 both represent lists of integers indexed from 0 to 99.

• arrl and arr2 both represent lists of integers indexed from 5 to 104.

• arrl represents a list of integers indexed from 0 to 104, and arr2 represents a list of integers indexed from 0 to 99.

• arrl represents a list of integers indexed from 5 to 99, and arr2 represents a list of integers indexed from 0 to 99.

• arrl represents a list of integers indexed from 5 to 104, and arr2 represents a list of integers indexed from 0 to 99.

Consider the following method, which is intended to return the number of strings of length greater than or equal to 3 in an array of String objects.
public static int checkString(String[] arr)
{
int count = 0;
for (int k = 0; k < arr.length; k++)
{
if (arr[k].length() >= 3)
{
count++;
}
}
return count;
}
Which of the following code segments compile without error?
checkString(new String[]);
checkString(new String[0]);
String[] str = {"cat", "dog"};checkString(str);

• II only

• III only

• I and III only

• II and III only

• I, II, and III

Consider the following instance variable and incomplete method. The method calcTotal is intended to return the sum of all values in vals.

private int[] vals;

public int calcTotal()

{

int total = 0;

/* missing code */

return total;

}

Which of the code segments shown below can be used to replace /* missing code */ so that calcTotal will work as intended?

I. for (int pos = 0; pos < vals.length; pos++)

{

total += vals[pos];

}

II. for (int pos = vals.length; pos > 0; pos--)

{

total += vals[pos];

}

III. int pos = 0;

while (pos < vals.length)

{

total += vals[pos];

pos++;

}

• I only

• II only

• III only

• I and III

• II and III

Consider the following two methods that appear within a single class.

public void changeIt(int[] list, int num)

{

list = new int[5];

num = 0;

for (int x = 0; x < list.length; x++)

list[x] = 0;

}

public void start()

{

int[] nums = {1, 2, 3, 4, 5};

int value = 6;

changeIt(nums, value);

for (int k = 0; k < nums.length; k++)

System.out.print(nums[k] + " ");

System.out.print(value);

}

What is printed as a result of the call start()?

• 0 0 0 0 0 0

• 0 0 0 0 0 6

• 1 2 3 4 5 6

• 1 2 3 4 5 0

The following incomplete method is intended to return the largest integer in the array numbers.

// precondition: numbers.length > 0

public static int findMax(int[]numbers)

{

int posOfMax = O;

for (int index = 1; index < numbers.length; index++)

{

if ( /*condition*/ )

{

/* statement */

}

}

return numbers[posOfMax];

}

Which of the following can be used to replace /* condition / and / statement */ so that findMax will work as intended?

• /* condition / / statement */

  numbers[index] > numbers[posOfMax]

  posOfMax = numbers[index];

• /* condition / / statement */

  numbers[index] > numbers[posOfMax]

  posOfMax = index;

• /* condition / / statement */

  numbers[index] > posOfMax

  posOfMax = numbers[index];

• /* condition / / statement */

  numbers[index] < posOfMax

  posOfMax = numbers[index];

• /* condition / / statement */

  numbers[index] < numbers[posOfMax]

  posOfMax = index;

The following question refer to the following information.

Consider the following data field and method. Method maxHelper is intended to return the largest value among the first numVals values in an array; however, maxHelper does not work as intended.

private int[] nums;

// precondition: 0 < numVals <= nums.length

private int maxHelper(int numVals)

{

Line 1: int max = maxHelper(numVals - 1);

Line 2: if (max > nums[numVals - 1])

return max;

else

return nums[numVals - 1];

}

Which of the following corrects the method maxHelper so that it works as intended?

• Insert the following statement before Line 1.

  if (numVals == 0)

  return numVals;

• Insert the following statement before Line 1.

  if (numVals == 1

  return nums[0];

• Insert the following statement between Line 1 and Line 2.

  if (numVals == 0)

  return numVals;

• Insert the following statement between Line 1 and Line 2.

  if (numVals == 1)

  return nums[0];

• Insert the following statement between Line 1 and Line 2.

  if (numVals < 2)

  return numVals;