AP计算机2009年考试：多项选择

3. AP计算机2009年考试：多项选择

Consider the following code segment.

int value = 15;  
while (value < 28)  
{  
    System.out.println(value);  
    value++;  
}

What are the first and last numbers output by the code segment?

15 27

15 28

16 27

16 28

16 29

A teacher put three bonus questions on a test and awarded 5 extra points to anyone who answered all three bonus questions correctly and no extra points otherwise. Assume that the boolean variables bonusOne, bonusTwo, and bonusThree indicate whether a student has answered the particular question correctly. Each variable was assigned true if the answer was correct and false if the answer was incorrect.

Which of the following code segments will properly update the variable grade based on a student’s performance on the bonus questions?

if (bonusOne && bonusTwo && bonusThree)  
    grade += 5;

II.

if (bonusOne || bonusTwo || bonusThree)  
    grade += 5;

III.

if (bonusOne)  
    grade += 5;  
if (bonusTwo)  
    grade += 5;  
if (bonusThree)  
    grade += 5;

I only

II only

III only

I and III

II and III

Assume that an array of integer values has been declared as follows and has been initialized.

int[] arr = new int[10];

Which of the following code segments correctly interchanges the value of arr[0] and arr[5]?

arr[0] = 5;

arr[5] = 0;

arr[0] = arr[5];

arr[5] = arr[0];

int k = arr[5];

arr[0] = arr[5];

arr[5] = k;

int k = arr[0];

arr[0] = arr[5];

arr[5] = k;

int k = arr[5];

arr[5] = arr[0];

arr[0] = arr[5];

Consider the following code segment.

ArrayList items = new ArrayList();  
items.add("A");  
items.add("B");  
items.add("C");  
items.add(0,"D");  
items.remove(3);  
items.add(0, "E");

What is printed as a result of executing the code segment?

[A, B, C, E]

[A, B, D, E]

[E, D, A, B]

[E, D, A, C]

[E, D, C, B]

When designing a class hierarchy, which of the following should be true of a superclass?

A superclass should contain the data and functionality that are common to all subclasses that inherit from the superclass.

A superclass should be the largest, most complex class from which all other subclasses are derived.

A superclass should contain the data and functionality that are only required for the most complex class.

A superclass should have public data in order to provide access for the entire class hierarchy.

A superclass should contain the most specific details of the class hierarchy.

int k = a random number such that 1 <= k <= n;  

for (int p = 2; p <= k; p++)  
    for (int r = 1; r < k; r++)  
        System.out.println("Hello");

What is the minimum number of times that Hello will be printed?

n-1

n-2

What is the maximum number of times that Hello will be printed?

n - 1

n - 2

(n - 1) * (n - 1)

n * n

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?

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 code segment.

String str = "abcdef";  
for (int rep = 0; rep < str.length() - 1; rep++)  
{  
    System.out.print(str.substring(rep, rep + 2));  
}

What is printed as a result of executing this code segment?

abcdef

aabbccddeeff

abbccddeef

abcbcdcdedef

Nothing is printed because an IndexOutOfBoundsException is thrown.

Consider the following method.

public void numberCheck(int maxNum)  
{  
    int typeA = 0;  
    int typeB = 0;  
    int typeC = 0;  

    for (int k = 1; k <= maxNum; k++)  
    {  
        if (k % 2 == 0 && k % 5 == 0)  
            typeA++;  
        if (k % 2 == 0)  
            typeB++;  
        if (k % 5 == 0)  
            typeC++;  
    }  

    System.out.println(typeA + " " + typeB + " " + typeC);  
}

What is printed as a result of the call numberCheck(50)?

5 20 5

5 20 10

5 25 5

5 25 10

30 25 10

Consider the following method that is intended to modify its parameter nameList by replacing all occurrences of name with newValue.

public void replace(ArrayList nameList,  
                String name, String newValue)  
{  
    for (int j = 0; j < nameList.size(); j++)  
    {  
        if ( /* expression */ )  
        {  
            nameList.set(j, newValue);  
        }  
    }  
}

Which of the following can be used to replace /* expression */ so that replace will work as intended?

nameList.get(j).equals(name)

nameList.get(j) == name

nameList.remove(j)

nameList[j] == name

nameList[j].equals(name)

Consider the following incomplete method.

public int someProcess(int n)  
{  
    /* body of someProcess */  
}

The following table shows several examples of input values and the results that should be produced by calling someProcess.

Input Value `n`	Value Returned by `someProcess(n)`
3	30
6	60
7	7
8	80
9	90
11	11
12	120
14	14
16	160

Which of the following code segments could be used to replace /* body of someProcess */ so that method will produce the results shown in the table?

if ((n % 3 == 0) && (n % 4 == 0))  
    return n * 10;  
else  
    return n;

II.

if ((n % 3 == 0) || (n % 4 == 0))  
    return n * 10;  

return n;

III.

if (n % 3 == 0)  
    if (n % 4 == 0)  
        return n * 10;  

return n;

I only

II only

III only

I and III

II and III

Consider the following method.

// precondition: x >= 0  
public void mystery(int x)  
{  
    if ((x / 10) != 0)  
    {  
        mystery(x / 10);  
    }  

    System.out.print(x % 10);  
}

Which of the following is printed as a result of the call mystery(123456)?

Many digits are printed due to infinite recursion

Consider the following instance variables and incomplete method that are part of a class that represents an item. The variables years and months are used to represent the age of the item, and the value for months is always between 0 and 11, inclusive. Method updateAge is used to update these variables based on the parameter extraMonths that represents the number of months to be added to the age.

private int years;  
private int months; // 0 <= months <= 11  

// precondition: extraMonths >= 0  
public void updateAge(int extraMonths)  
{  
    /* body of updateAge */  
}

Which of the following code segments could be used to replace /* body of updateAge */ so that the method will work as intended?

int yrs = extraMonths % 12;  
int mos = extraMonths / 12;  

years = years + yrs;  
month = months + mos;

II.

int totalMonths = years * 12 + months + extraMonths;  
years = totalMonths / 12;  
months = totalMonths % 12;

III.

int totalMonths = months + extraMonths;  
years = years + totalMonths / 12;  
months = totalMonths % 12;

I only

II only

III only

II and III only

I, II, and III

Consider the following method.

public String inRangeMessage(int value)  
{  
    if (value < 0 || value > 100)  
        return "Not in range";  
    else  
        return "In range";  
}

Consider the following code segments that could be used to replace the body of inRangeMessage.

if (value < 0)  
{  
    if (value > 100)  
        return "Not in range";  
    else  
        return "In range";  
}  
else  
    return "In range";

II.

if (value < 0)  
    return "Not in range";  
else if (value > 100)  
    return "Not in range";  
else  
    return "In range";

III.

if (value >= 0)  
    return "In range";  
else if (value <= 100)  
    return "In range";  
else  
    return "Not in range";

Which of the replacements will have the same behavior as the original version of inRangeMessage?

I only

II only

III only

I and III

II and III

Consider the following class declaration.

public class SomeClass  
{  
    private int num;  

    public SomeClass(int n)  
    {  
        num = n;  
    }  

    public void increment(int more)  
    {  
        num = num + more;  
    }  

    public int getNum()  
    {  
        return num;  
    }  
}

The following code segment appears in another class.

SomeClass one = new SomeClass(100);  
SomeClass two = new SomeClass(100);  
SomeClass three = one;  

one.increment(200);  

System.out.println(one.getNum() + " " + two.getNum() + " " +  
                three.getNum());

What is printed as a result of executing the code segment?

100 100 100

300 100 100

300 100 300

300 300 100

300 300 300

The following incomplete method is intended to sort its array parameter arr in increasing order.

// postcondition: arr is sorted in increasing order  
public static void sortArray(int[] arr)  
{  
    int j, k;  

    for (j = arr.length - 1; j > 0; j--)  
    {  
        int pos = j;  

        for ( /* missing code */ )  
        {  
            if (arr[k] > arr[pos])  
            {  
                pos = k;  
            }  
        }  
        swap(arr, j, pos);  
    }  
}

Assume that swap(arr, j, pos) exchange the values of arr[j] and arr[pos]. Which of the following could be used to replace /* missing code */ so that executing the code segment sorts the values in array arr?

k = j - 1; k > 0; k--

k = j - 1; k >= 0; k--

k = 1; k < arr.length; k++

k = 1; k > arr.length; k++

k = 0; k <= arr.length; k++

Assume that x and y are boolean variables and have been properly initialized.

(x && y) || !(x && y)

The result of evaluating the expression above is best described as

always true

always false

true only when x is true and y is true

true only when x and y have the same value

true only when x and y have different values

Assume that the following variable declarations have been made.

double d = Math.random();

double r;

Which of the following assigns a value to r from the uniform distribution over the range 0.5 <= r < 5.5?

r = d + 0.5;

r = d + 0.5 * 5.0;

r = d * 5.0;

r = d * 5.0 + 0.5;

r = d * 5.5;

Consider the following instance variables and method that appear in a class representing student information.

private int assignmentsCompleted;  
private double testAverage;  

public boolean isPassing()  
{ /* implementation not shown */ }

A student can pass a programming course if at least one of the following conditions is met.

The student has a test average that is greater than or equal to 90.
The student has a test average that is greater than or equal to 75 and has at least 4 completed assignments.

Consider the following proposed implementations of the isPassing method.

if (testAverage >= 90)  
    return true;  
if (testAverage >= 75 && assignmentsCompleted >= 4)  
    return true;  
return false;

II.

boolean pass = false;  
if (testAverage >= 90)  
    pass = true;  
if (testAverage >= 75 && assignmentsCompleted >= 4)  
    pass = true;  
return pass;

III.

return (testAverage >= 90) ||  
        (testAverage >= 75 && assignmentsCompleted >= 4);

Which of the implementations will correctly implement method isPassing?

I only

II only

I and III only

II and III only

I, II, and III

21-25题涉及当前已被移出考试范围的GridWorld case study。

Consider the following code segment.

int k = 0;  
while (k < 10)  
{  
    System.out.print((k % 3) + " ");  
    if ((k % 3) == 0)  
        k = k + 2;  
    else  
        k++;  
}

What is printed as a result of executing the code segment?

0 2 1 0 2

0 2 0 2 0 2

0 2 1 0 2 1 0

0 2 0 2 0 2 0

0 1 2 1 2 1 2

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?

false if ((arr[k] % 2) == 0)isEven = true;

false if ((arr[k] % 2) != 0)isEven = false; else isEven = true;

true if ((arr[k] % 2) != 0)isEven = false;

true if ((arr[k] % 2) != 0)isEven = false; else isEven = true;

true if ((arr[k] % 2) == 0)isEven = false; else isEven = true;

Consider the following code segment.

int x = /* some integer value */;  
int y = /* some integer value */;  

boolean result = (x < y);  

result = ( (x >= y) && !result );

Which of the following best describes the conditions under which the value of result will be true after the code segment is executed?

Only when x < y

Only when x >= y

Only when x and y are equal

The value will always be true

The value will never be true

Consider the following code segment.

for (int outer = 0; outer < n; outer++)  
{  
    for (int inner = 0; inner <= outer; inner++)  
    {  
        System.out.print(outer + " ");  
    }  
}

if n has been declared as an integer with the value 4, what is printed as a result of executing the code segment?

0 1 2 3

0 0 1 0 1 2

0 1 2 2 3 3 3

0 1 1 2 2 2 3 3 3 3

0 0 1 0 1 2 0 1 2 3

Consider the following class declarations.

public class Base  
{  
    private int myVal;  

    public Base()  
    { myVal = 0; }  

    public Base(int x)  
    { myVal = x; }  
}  

public class Sub extends Base  
{  
    public Sub()  
    { super(0); }  
}

Which of the following statements will NOT compile?

Base b1 = new Base();

Base b2 = new Base(5);

Base s1 = new Sub();

Sub s2 = new Sub();

Sub s3 = new Sub(5);

Assume that a and b are variables of type int. The expression

!(a < b) && !(a > b)

is equivalent to which of the following?

true

false

a == b

a != b

!(a < b) && (a > b)

Consider the following code segment.

int a = 24;  
int b = 30;  
while (b != 0)  
{  
    int r = a % b;  
    a = b;  
    b = r;  
}  

System.out.println(a);

What is printed as a result of executing the code segment?

Consider the following method.

public int sol(int lim)  
{  
    int s = 0;  

    for (int outer = 1; outer <= lim; outer++)  
    {  
        for (int inner = outer; inner <= lim; inner++)  
        {  
            s++;  
        }  
    }  

    return s;  
}

What values is returned as a result of the call sol(10)?

Consider the following incomplete method. Method findNext is intended to return the index of the first occurrence of the value val beyond the position start in array arr.

// returns index of first occurrence of val in arr  
// after position start;  
// returns arr.length if val is not found  
public int findNext(int[] arr, int val, int start)  
{  
    int pos = start + 1;  

    while ( /* condition */ )  
        pos++;  

    return pos;  
}

For example, consider the following code segment.

int[] arr = {11, 22, 100, 33, 100, 11, 44, 100};

System.out.println(findNext(arr, 100, 2));

The execution of the code segment should result in the value 4 being printed.

Which of the following expressions could be used to replace /* condition */ so that findNext will work as intended?

(pos < arr.length) && (arr[pos] != val)

(arr[pos] != val) && (pos < arr.length)

(pos < arr.length) || (arr[pos] != val)

(arr[pos] == val) && (pos < arr.length)

(pos < arr.length) || (arr[pos] == val)

Consider the following code segments.

int k = 1;  
while (k < 20)  
{  
    if (k % 3 == 1)  
        System.out.print(k + " ");  

    k = k + 3;  
}

II.

for (int k = 1; k < 20; k++)  
{  
    if (k % 3 == 1)  
        System.out.print(k + " ");  
}

III.

for (int k = 1; k < 20; k = k + 3)  
{  
    System.out.print(k + " ");  
}

Which of the code segments above will produce the following output?

1 4 7 10 13 16 19

I only

II only

I and II only

II and III only

I, 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

“changeIt“ will throw an exception.

Consider the following declaration of the class NumSequence, which has a constructor that is intended to initialize the instance variable seq to an ArrayList of numberOfValues random floating-point values in the range [0.0, 1.0).

public class NumSequence  
{  
    private ArrayList seq;  

    // precondition: numberOfValues > 0  
    // postcondition: seq has been initialized to an ArrayList of  
    //                length numberOfValues; each element of seq  
    //                contains a random Double in the range [0.0, 1.0)  
    public NumSequence(int numberOfValues)  
    {  
        /* missing code */  
    }  
}

Which of the following code segments could be used to replace /* missing code */ so that the constructor will work as intended?

ArrayList seq = new ArrayList();  
for (int k = 0; k < numberOfValues; k++)  
    seq.add(new Double(Math.random()));

II.

seq = new ArrayList();  
for (int k = 0; k < numberOfValues; k++)  
    seq.add(new Double(Math.random()));

III.

ArrayList temp = new ArrayList();  
for (int k = 0; k < numberOfValues; k++)  
    seq.add(new Double(Math.random()));  

seq = temp;

II only

III only

I and II

I and III

II and III

Consider the following code segment.

double a = 1.1;  
double b = 1.2;  

if ((a + b) * (a - b) != (a * a) - (b * b))  
{  
    System.out.println("Mathematical error!");  
}

Which of the following best describes why the phrase "Mathematical error!" would be printed? (Remember that mathematically (a+b)∗(a−b)=a^2−b^2.)

Precedence rules make the if condition true.

Associativity rules make the if condition true.

Roundoff error makes the if condition true.

Overflow makes the if condition true.

A compiler bug or hardware error has occurred.

Consider the following recursive method.

public static String recur(int val)  
{  
    String dig = " " + (val % 3);  

    if (val / 3 > 0)  
        return dig + recur(val / 3);  

    return dig;  
}

What is printed as a result of executing the following statement?

System.out.println(recur(32));

Consider the following method.

public String goAgain(String str, int index)  
{  
    if (index >= str.length())  
        return str;  

    return str + goAgain(str.substring(index), index + 1);  
}

What is printed as a result of executing the following statement?

System.out.println(goAgain("today", 1));

today

todayto

todayoday

todayodayay

todayodaydayayy