Quiz CH7 && CH12.11 (?)

Indicate true or false for the following statements: (a) Every element in an array has the same type. (b) The array size is fixed after an array reference variable is declared (c) The array size is fixed after it is created. (d) The elements in an array must be of a primitive data type.

(a) Answer: True(b) Answer: False(c) Answer: True(d) Answer: False

Write statements to do the following: a. Create an array to hold 10 double values. b. Assign the value 5.5 to the last element in the array. c. Display the sum of the first two elements. d. Write a loop that computes the sum of all elements in the array. e. Write a loop that finds the minimum element in the array. f. Randomly generate an index and display the element of this index in the array. g. Use an array initializer to create another array with the initial values 3.5, 5.5, 4.52, and 5.6.

(a) double[] list = new double[10]; (b) list[list.length - 1] = 5.5; (c) System.out.println(list[0] + list[1]); (d) double sum = 0; for (int i = 0; i < list.length; i++) sum += list[i]; (e) double min = list[0]; for (int i = 1; i < list.length; i++) if (min > list[i]) min = list[i]; (f) System.out.println(list[(int)(Math.random() * list.length)]); (g) double[] list = {3.5, 5.5, 4.52, 5.6};

Show the output of the following two programs: (a) public class Test { public static void main(String[] args) { int number = 0; int[] numbers = new int[1]; m(number, numbers); System.out.println("number is " + number + " and numbers[0] is " + numbers[0]); } public static void m(int x, int[] y) { x = 3; y[0] = 3; } } (b) public class Test { public static void main(String[] args) { int[] list = {1, 2, 3, 4, 5}; reverse(list); for (int i = 0; i < list.length; i++) System.out.print(list[i] + " "); } public static void reverse(int[] list) { int[] newList = new int[list.length]; for (int i = 0; i < list.length; i++) newList[i] = list[list.length - 1 - i]; list = newList; } }

(a) number is 0 and numbers[0] is 3 (b) 1 2 3 4 5

For the linear search method in the text, what is linearSearch(new int[]{1, 2, 14, 7, 3}, 4)?

-1

What is java.util.Arrays.binarySearch(new int[]{1, 2, 3, 7, 14}, 5)?

-4

What is the output of the following code? 1 public class Test { 2 public static void main(String[] args) { 3 int list[] = {1, 2, 3, 4, 5, 6}; 4 for (int i = 1; i < list.length; i++) 5 list[i] = list[i - 1]; 6 7 for (int i = 0; i < list.length; i++) 8 System.out.print(list[i] + " "); 9 } 10 }

1 1 1 1 1 1

What is the output of the following code? public class Test { public static void main(String[] args) { int[] x = {1, 2}; int i = 1; m(i, x); System.out.print(i + "," + x[0]); } public static void m(int i, int[] list) { i = 9; list[0] = 9; } }

1,9

What is the output of the following code? public class Test { public static void main(String[] args) { int[] list1 = {1, 2, 3}; int[] list2 = list1; list2[1] = 10; System.out.println(list1[1]); } }

10

What is java.util.Arrays.binarySearch(new int[]{1, 2, 3, 7, 14}, 7)?

3

For the linear search method in the text, what is linearSearch(new int[]{1, 2, 14, 7, 3}, 3)?

4

Suppose int[] list = {4, 5, 6, 2, 1, 0}, what is list[0]?

4

Suppose int[] list = {4, 5, 6, 2, 1, 0}, what is list.length?

6

What happens when your program attempts to access an array element with an invalid index?

A runtime exception ArrayIndexOutOfBounds occurs.

Analyze the following code: public class Test { public static void main(String[] args) { int[] x = {1, 2, 3, 4}; int[] y = x;x = new int[2]; for (int i = 0; i < y.length; i++) System.out.print(y[i] + " "); } } A. The program displays 1 2 3 4 B. The program displays 0 0 C. The program displays 0 0 3 4 D. The program displays 0 0 0 0

A. The program displays 1 2 3 4

Analyze the following code: public class Test { public static void main(String[] args) { int[] oldList = {1, 2, 3, 4, 5}; reverse(oldList); for (int i = 0; i < oldList.length; i++) System.out.print(oldList[i] + " "); } public static void reverse(int[] list) { int[] newList = new int[list.length]; for (int i = 0; i < list.length; i++) newList[i] = list[list.length - 1 - i];list = newList; } } A. The program displays 1 2 3 4 5. B. The program displays 1 2 3 4 5 and then raises an ArrayIndexOutOfBoundsException. C. The program displays 5 4 3 2 1. D. The program displays 5 4 3 2 1 and then raises an ArrayIndexOutOfBoundsException.

A. The program displays 1 2 3 4 5. Explanation: The contents of the array oldList have not been changed as result of invoking the reverse method.

What is the representation of the third element in an array called a? A. a[2] B. a(2) C. a[3] D. a(3)

A. a[2]

Suppose int i = 5, which of the following can be used as an index for array double[] t = new double[100]?

A. i B. (int)(Math.random() * 100)) C. i + 10

Which of the following statements are correct to invoke the printMax method in Listing 7.5 in the textbook? A. printMax(1, 2, 2, 1, 4); B. printMax(new double[]{1, 2, 3}); C. printMax(1.0, 2.0, 2.0, 1.0, 4.0); D. printMax(new int[]{1, 2, 3});

A. printMax(1, 2, 2, 1, 4); B. printMax(new double[]{1, 2, 3}); C. printMax(1.0, 2.0, 2.0, 1.0, 4.0); The last one printMax(new int[]{1, 2, 3}); is incorrect, because the array must of the double[] type.

What is the output of the following code? double[] myList = {1, 5, 5, 5, 5, 1}; double max = myList[0]; int indexOfMax = 0; for (int i = 1; i < myList.length; i++) { if (myList[i] > max) { max = myList[i]; indexOfMax = i; } } System.out.println(indexOfMax); A. 0 B. 1 C. 2 D. 3 E. 4

B. 1

What is output of the following code: public class Test { public static void main(String[] args) { int[] x = {120, 200, 016}; for (int i = 0; i < x.length; i++) System.out.print(x[i] + " "); } } A. 120 200 16 B. 120 200 14 C. 120 200 20 D. 016 is a compile error. It should be written as 16.

B. 120 200 14 Explanation: 016 is an octal number. The prefix 0 indicates that a number is in octal.

If you declare an array double[] list = {3.4, 2.0, 3.5, 5.5}, list[1] is ________. A. 3.4 B. 2.0 C. 3.5 D. 5.5 E. undefined

B. 2.0

How many elements are in array double[] list = new double[5]? A. 4 B. 5 C. 6 D. 0

B. 5

Analyze the following code: public class Test { public static void main(String[] args) { int[] x = {1, 2, 3, 4}; int[] y = x;x = new int[2]; for (int i = 0; i < x.length; i++) System.out.print(x[i] + " "); } } A. The program displays 1 2 3 4 B. The program displays 0 0 C. The program displays 0 0 3 4 D. The program displays 0 0 0 0

B. The program displays 0 0

Assume int[] scores = {1, 20, 30, 40, 50}, what is the output of System.out.println(java.util.Arrays.toString(scores))? A. {1, 20, 30, 40, 50} B. [1, 20, 30, 40, 50] C. {1 20 30 40 50} D. [1 20 30 40 50]

B. [1, 20, 30, 40, 50]

Which of the following statements is valid? A. int i = new int(30); B. double d[] = new double[30]; C. int[] i = {3, 4, 3, 2}; D. char[] c = new char(); E. char[] c = new char[4]{'a', 'b', 'c', 'd'};

B. double d[] = new double[30]; C. int[] i = {3, 4, 3, 2}; Explanation: e would be corrected if it is char[] c = new char[]{'a', 'b', 'c', 'd'};

The JVM stores the array in an area of memory, called _______, which is used for dynamic memory allocation where blocks of memory are allocated and freed in an arbitrary order. A. stack B. heap C. memory block D. dynamic memory

B. heap

If a key is not in the list, the binarySearch method returns _________. A. insertion point B. insertion point - 1 C. -(insertion point + 1) D. -insertion point

B. insertion point - 1

Use the selectionSort method presented in this section to answer this question. What is list1 after executing the following statements?double[] list1 = {3.1, 3.1, 2.5, 6.4};selectionSort(list1); A. list1 is 3.1, 3.1, 2.5, 6.4 B. list1 is 2.5 3.1, 3.1, 6.4 C. list1 is 6.4, 3.1, 3.1, 2.5 D. list1 is 3.1, 2.5, 3.1, 6.4

B. list1 is 2.5 3.1, 3.1, 6.4

The reverse method is defined in the textbook. What is list1 after executing the following statements? int[] list1 = {1, 2, 3, 4, 5, 6}; list1 = reverse(list1); A. list1 is 1 2 3 4 5 6 B. list1 is 6 5 4 3 2 1 C. list1 is 0 0 0 0 0 0 D. list1 is 6 6 6 6 6 6

B. list1 is 6 5 4 3 2 1

The reverse method is defined in this section. What is list1 after executing the following statements? int[] list1 = {1, 2, 3, 4, 5, 6}; int[] list2 = reverse(list1); A. list1 is 1 2 3 4 5 6 B. list1 is 6 5 4 3 2 1 C. list1 is 0 0 0 0 0 0 D. list1 is 6 6 6 6 6 6

B. list1 is 6 5 4 3 2 1

In the following code, what is the output for list2? public class Test { public static void main(String[] args) { int[] list1 = {1, 2, 3}; int[] list2 = {1, 2, 3}; list2 = list1;list1[0] = 0; list1[1] = 1; list2[2] = 2; for (int i = 0; i < list1.length; i++) System.out.print(list1[i] + " "); } } A. 1 2 3 B. 1 1 1 C. 0 1 2 D. 0 1 3

C. 0 1 2

In the following code, what is the output for list2? public class Test { public static void main(String[] args) { int[] list1 = {1, 2, 3}; int[] list2 = {1, 2, 3}; list2 = list1;list1[0] = 0; list1[1] = 1; list2[2] = 2; for (int i = 0; i < list2.length; i++) System.out.print(list2[i] + " "); } } A. 1 2 3 B. 1 1 1 C. 0 1 2 D. 0 1 3

C. 0 1 2

Assume int[] t = {1, 2, 3, 4}. What is t.length?

C. 4

Analyze the following code. int[] list = new int[5]; list = new int[6]; A. The code has compile errors because the variable list cannot be changed once it is assigned. B. The code has runtime errors because the variable list cannot be changed once it is assigned. C. The code can compile and run fine. The second line assigns a new array to list. D. The code has compile errors because you cannot assign a different size array to list.

C. The code can compile and run fine. The second line assigns a new array to list.

Analyze the following code: public class Test { public static void main(String[] args) { double[] x = {2.5, 3, 4}; for (double value: x) System.out.print(value + " "); } } A. The program displays 2.5, 3, 4 B. The program displays 2.5 3 4 C. The program displays 2.5 3.0 4.0 D. The program displays 2.5, 3.0 4.0 E. The program has a syntax error because value is undefined.

C. The program displays 2.5 3.0 4.0

Analyze the following code: public class Test { public static void main(String[] args) { int[] a = new int[4]; a[1] = 1;a = new int[2]; System.out.println("a[1] is " + a[1]); } } A. The program has a compile error because new int[2] is assigned to a. B. The program has a runtime error because a[1] is not initialized. C. The program displays a[1] is 0. D. The program displays a[1] is 1.

C. The program displays a[1] is 0. Explanation: After executing the statement a = new int[2], a refers to int[2]. The default value for a[0] and a[1] is 0.

Analyze the following code: public class Test1 { public static void main(String[] args) { xMethod(new double[]{3, 3}); xMethod(new double[5]); xMethod(new double[3]{1, 2, 3}); } public static void xMethod(double[] a){ System.out.println(a.length); } } A. The program has a compile error because xMethod(new double[]{3, 3}) is incorrect. B. The program has a compile error because xMethod(new double[5]) is incorrect. C. The program has a compile error because xMethod(new double[3]{1, 2, 3}) is incorrect. D. The program has a runtime error because a is null.

C. The program has a compile error because xMethod(new double[3]{1, 2, 3}) is incorrect. Explanation: new double[3]{1, 2, 3} should be replaced by new double[]{1, 2, 3}) (anonymous array).

Analyze the following code: public class Test { public static void main(String[] args) { final int[] x = {1, 2, 3, 4}; int[] y = x;x = new int[2]; for (int i = 0; i < y.length; i++) System.out.print(y[i] + " "); } } A. The program displays 1 2 3 4 B. The program displays 0 0 C. The program has a compile error on the statement x = new int[2], because x is final and cannot be changed. D. The elements in the array x cannot be changed, because x is final.

C. The program has a compile error on the statement x = new int[2], because x is final and cannot be changed. The value stored in x is final, but the values in the array are not final. x is a constant reference variable that points to an array with four elements Because it is a constant, you cannot create a new reference variable x that points to a different array, but you can change the value of the elements in the array, e.g. x[1] could be changed to 10 instead of 2.

Analyze the following code: public class Test { public static void main(String[] args) { int[] x = new int[5]; int i; for (i = 0; i < x.length; i++) x[i] = i; System.out.println(x[i]); } } A. The program displays 0 1 2 3 4. B. The program displays 4. C. The program has a runtime error because the last statement in the main method causes ArrayIndexOutOfBoundsException. D. The program has a compile error because i is not defined in the last statement in the main method.

C. The program has a runtime error because the last statement in the main method causes ArrayIndexOutOfBoundsException. Explanation: After the for loop i is 5. x[5] is out of bounds.

Analyze the following code. public class Test { public static void main(String[] args) { int[] x = new int[3]; System.out.println("x[0] is " + x[0]); } } A. The program has a compile error because the size of the array wasn't specified when declaring the array. B. The program has a runtime error because the array elements are not initialized. C. The program runs fine and displays x[0] is 0. D. The program has a runtime error because the array element x[0] is not defined.

C. The program runs fine and displays x[0] is 0.

How can you initialize an array of two characters to 'a' and 'b'?

C. char[] charArray = {'a', 'b'}; D. char[] charArray = new char[]{'a', 'b'};

What is the correct term for numbers[99]? A. index B. index variable C. indexed variable D. array variable E. array

C. indexed variable

Which of the following is incorrect? A. int[] a = new int[2]; B. int a[] = new int[2]; C. int[] a = new int(2); D. int a = new int[2]; E. int a() = new int[2];

C. int[] a = new int(2); D. int a = new int[2]; E. int a() = new int[2];

The __________ method sorts the array scores of the double[] type. A. java.util.Arrays(scores) B. java.util.Arrays.sorts(scores) C. java.util.Arrays.sort(scores) D. Njava.util.Arrays.sortArray(scores)

C. java.util.Arrays.sort(scores)

When you pass an array to a method, the method receives __________. A. a copy of the array B. a copy of the first element C. the reference of the array D. the length of the array

C. the reference of the array

When you return an array from a method, the method returns __________. A. a copy of the array B. a copy of the first element C. the reference of the array D. the length of the array

C. the reference of the array

What is output of the following code: public class Test { public static void main(String[] args) { int list[] = {1, 2, 3, 4, 5, 6}; for (int i = 1; i < list.length; i++) list[i] = list[i - 1];for (int i = 0; i < list.length; i++) System.out.print(list[i] + " "); } } A. 1 2 3 4 5 6 B. 2 3 4 5 6 6 C. 2 3 4 5 6 1 D. 1 1 1 1 1 1

D. 1 1 1 1 1 1

What is the output of the following code? int[] myList = {1, 2, 3, 4, 5, 6}; for (int i = myList.length - 2; i >= 0; i--) { myList[i + 1] = myList[i]; } for (int e: myList) System.out.print(e + " "); A. 1 2 3 4 5 6 B. 6 1 2 3 4 5 C. 6 2 3 4 5 1 D. 1 1 2 3 4 5 E. 2 3 4 5 6 1

D. 1 1 2 3 4 5

Assume int[] scores = {1, 20, 30, 40, 50}, what value does java.util.Arrays.binarySearch(scores, 30) return? A. 0 B. -1 C. 1 D. 2 E. -2

D. 2

Show the output of the following code: public class Test { public static void main(String[] args) { int[] x = {1, 2, 3, 4, 5}; increase(x); int[] y = {1, 2, 3, 4, 5}; increase(y[0]); System.out.println(x[0] + " " + y[0]); } public static void increase(int[] x) { for (int i = 0; i < x.length; i++) x[i]++; } public static void increase(int y) { y++; } } A. 0 0 B. 1 1 C. 2 2 D. 2 1 E. 1 2

D. 2 1 Explanation: Invoking increase(x) passes the reference of the array to the method. Invoking increase(y[0]) passes the value 1 to the method. The value y[0] outside the method is not changed.

If you declare an array double[] list = {3.4, 2.0, 3.5, 5.5}, the highest index in array list is __________. A. 0 B. 1 C. 2 D. 3 E. 4

D. 3

Which of the following declarations are correct? A. public static void print(String... strings, double... numbers) B. public static void print(double... numbers, String name) C. public static double... print(double d1, double d2) D. public static void print(double... numbers) E. public static void print(int n, double... numbers)

D. public static void print(double... numbers) E. public static void print(int n, double... numbers) Explanation: Only one variable-length parameter may be specified in a method and this parameter must be the last parameter. The method return type cannot be a variable-length parameter.

Suppose a method p has the following heading: public static int[] p() What return statement may be used in p()? A. return 1; B. return {1, 2, 3}; C. return int[]{1, 2, 3}; D. return new int[]{1, 2, 3};

D. return new int[]{1, 2, 3};

Assume int[] scores = {1, 20, 30, 40, 50}, what value does java.util.Arrays.binarySearch(scores, 3) return? A. 0 B. -1 C. 1 D. 2 E. -2

E. -2 Explanation: The binarySearch method returns the index of the search key if it is contained in the list. Otherwise, it returns ?insertion point - 1. The insertion point is the point at which the key would be inserted into the list. In this case the insertion point is 1. Note that the array index starts from 0.

Use the selectionSort method presented in this section to answer this question. Assume list is {3.1, 3.1, 2.5, 6.4, 2.1}, what is the content of list after the first iteration of the outer loop in the method? A. 3.1, 3.1, 2.5, 6.4, 2.1 B. 2.5, 3.1, 3.1, 6.4, 2.1 C. 2.1, 2.5, 3.1, 3.1, 6.4 D. 3.1, 3.1, 2.5, 2.1, 6.4 E. 2.1, 3.1, 2.5, 6.4, 3.1

E. 2.1, 3.1, 2.5, 6.4, 3.1

What would be the result of attempting to compile and run the following code? public class Test { public static void main(String[] args) { double[] x = new double[]{1, 2, 3}; System.out.println("Value is " + x[1]); } } A. The program has a compile error because the syntax new double[]{1, 2, 3} is wrong and it should be replaced by {1, 2, 3}. B. The program has a compile error because the syntax new double[]{1, 2, 3} is wrong and it should be replaced by new double[3]{1, 2, 3}; C. The program has a compile error because the syntax new double[]{1, 2, 3} is wrong and it should be replaced by new double[]{1.0, 2.0, 3.0}; D. The program compiles and runs fine and the output "Value is 1.0" is printed. E. The program compiles and runs fine and the output "Value is 2.0" is printed.

E. The program compiles and runs fine and the output "Value is 2.0" is printed. Explanation: new double[]{1, 2, 3} is correct. This is the syntax I have not covered in this edition, but will be covered in the future edition. In this question, double[] x = new double[]{1, 2, 3} is equivalent to double[] x = {1, 2, 3};

True or false? When an array is passed to a method, a new array is created and passed to the method.

False. When an array is passed to a method, the reference value of the array is passed. No new array is created. Both argument and parameter point to the same array.

Identify and fix the errors in the following code: 1 public class Test { 2 public static void main(String[] args) { 3 double[100] r; 4 5 for (int i = 0; i < r.length(); i++); 6 r(i) = Math.random * 100; 7 } 8 }

Line 3: the array declaration is wrong. It should be double[]. The array needs to be created before its been used. e.g. new double[10] Line 5: The semicolon (;) at the end of the for loop heading should be removed. Line 5: r.length() should be r.length. Line 6: random should be random() Line 6: r(i) should be r[i].

Will the program pick four random cards if you replace lines 22-27 in Listing 7.2 DeckOfCards.java with the following code? for (int i = 0; i < 4; i++) { int cardNumber = (int)(Math.random() * deck.length); String suit = suits[cardNumber / 13]; String rank = ranks[cardNumber % 13]; System.out.println("Card number " + cardNumber + ": " + rank + " of " + suit); }

No. You may have the same card appearing more than once.

What is wrong with each of the following method headers? public static void print(String... strings, double... numbers) public static void print(double... numbers, String name) public static double... print(double d1, double d2)

Only one variable-length parameter may be specified in a method and this parameter must be the last parameter. The method return type cannot be a variable-length parameter.

If high is a very large integer such as the maximum int value 2147483647, (low + high) / 2 may cause overflow. How do you fix it to avoid overflow?

Replace (low + high) / 2 with (-low + high) / 2 + low

Write a statement to declare a variable named x for an array of double values.

Suppose int[] list = {4, 5, 6, 2, 1, 0}, what is list.length?

Use the arraycopy method to copy the following array to a target array t: int[] source = {3, 4, 5};

System.arraycopy(source, 0, t, 0, source.length);

What is the array index type? What is the lowest index? What is the representation of the third element in an array named a?

The array index type is int and its lowest index is 0. a[2]

If the binary search method returns -4, is the key in the list? Where should the key be inserted if you wish to insert the key into the list?

The key is not in the list. The key should be inserted at -(-4 + 1) = 3.

Can you invoke the printMax method in Listing 7.5 using the following statements? printMax(1, 2, 2, 1, 4); printMax(new double[]{1, 2, 3}); printMax(new int[]{1, 2, 3});

The last oneprintMax(new int[]{1, 2, 3}); is incorrect, because the array must of the double[] type.

When is the memory allocated for an array?

The memory is allocated when an array is created.

Do the following two programs produce the same result? Program I: public class Test { public static void main(String[] args) { int[] list = {1, 2, 3, 4, 5}; reverse(list); for (int i = 0; i < list.length; i++) System.out.print(list[i] + " "); } public static void reverse(int[] list) { int[] newList = new int[list.length]; for (int i = 0; i < list.length; i++) newList[i] = list[list.length - 1 - i]; list = newList; } } Program II: public class Test { public static void main(String[] args) { int[] oldList = {1, 2, 3, 4, 5}; reverse(oldList); for (int i = 0; i < oldList.length; i++) System.out.print(oldList[i] + " "); } public static void reverse(int[] list) { int[] newList = new int[list.length]; for (int i = 0; i < list.length; i++) newList[i] = list[list.length - 1 - i]; list = newList; } } A. Yes B. No

Yes

How do you access elements in an array?

You access an array using its index. arrayRefVar[index] is known as an array indexed variable.

What is java.util.Arrays.toString(new int[]{1, 2, 3, 7, 14})?

[1, 2, 3, 7, 14]

What is java.util.Arrays.equals(new int[]{1, 2, 3, 7, 14}, new int[]{1, 2, 3, 14, 7})?

false

Which of the following statements are valid? int i = new int(30); double d[] = new double[30]; char[] r = new char(1..30); int i[] = (3, 4, 3, 2); float f[] = {2.3, 4.5, 6.6}; char[] c = new char();

int i = new int(30); Answer: Invalid double d[] = new double[30]; Answer: Valid char[] r = new char(1..30); Answer: Invalid int i[] = (3, 4, 3, 2); Answer: Invalid float f[] = {2.3, 4.5, 5.6}; Answer: Valid char[] c = new char(); Answer: Invalid

Write an expression for creating an array of the int type with size 40.

new int [40]

What is the output of the following code? int x = 30; int[] numbers = new int[x]; x = 60; System.out.println("x is " + x); System.out.println("The size of numbers is " + numbers.length);

x is 60 The size of numbers is 30