Ch. 6 Single-Dimensional Arrays

6.10 How can you initialize an array of two characters to 'a' and 'b'? A. char[] charArray = new char[2]; charArray = {'a', 'b'}; B. char[2] charArray = {'a', 'b'}; C. char[] charArray = {'a', 'b'}; D. char[] charArray = new char[]{'a', 'b'};

CD

6.16 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

6.26 The __________ method copies the sourceArray to the targetArray. A. System.copyArrays(sourceArray, 0, targetArray, 0, sourceArray.length); B. System.copyarrays(sourceArray, 0, targetArray, 0, sourceArray.length); C. System.arrayCopy(sourceArray, 0, targetArray, 0, sourceArray.length); D. System.arraycopy(sourceArray, 0, targetArray, 0, sourceArray.length);

D

6.34 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

6.4 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

Section 6.10 Searching Arrays 6.39 For the binarySearch method in Section 6.9.2, what is low and high after the first iteration of the while loop when invoking binarySearch(new int[]{1, 4, 6, 8, 10, 15, 20}, 11)? A. low is 0 and high is 6 B. low is 0 and high is 3 C. low is 3 and high is 6 D. low is 4 and high is 6 E. low is 0 and high is 5

D

6.11 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

Section 6.11 Sorting Arrays 6.41 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

6.32 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

6.46 Assume int[] list1 = {3, 4, 1, 9, 13}, int[] list2 = {3, 4, 1, 9, 13}, and int[] list3 = {4, 3, 1, 9, 13}, what is System.out.println(java.util.Arrays.equals(list1, list2) + " " + java.util.Arrays.equals(list1, list3)); A. true true B. true false C. false true D. false fasle

B

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

B

6.12 Assume int[] t = {1, 2, 3, 4}. What is t.length? A. 0 B. 3 C. 4 D. 5

C

6.14 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

6.15 (for-each loop) 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

6.40 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

C

6.18 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

6.28 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 - The correct answer is D 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.

Section 6.9 Variable-Length Argument Lists 6.37 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)

DE - The correct answer is DE 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.

6.21 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

6.29 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

A

6.36 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

A

Sections 6.2 Array Basics 6.1 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

6.13 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

6.17 (Tricky) 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

6.2 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

6.22 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

6.35 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

6.42 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

6.9 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'};

BC The correct answer is BC Explanation: e would be corrected if it is char[] c = new char[]{'a', 'b', 'c', 'd'};

6.20 What will be displayed by the following code? 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

6.24 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

6.47 Assume int[] scores = {3, 4, 1, 9, 13}, which of the following statement displays all the element values in the array? A. System.out.println(scores); B. System.out.println(scores.toString()); C. System.out.println(java.util.Arrays.toString(scores)); D. System.out.println(scores[0]);

C

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

C

6.8 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

Section 6.12 The Arrays Class 6.43 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

Section 6.5 Copying Arrays 6.19 What will be displayed by the following code? 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

Section 6.6 Passing Arrays to Methods 6.27 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

Section 6.7 Returning an Array from a Method 6.33 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

6.25 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 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.

6.3 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,D,E

6.44 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

2

6.30 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 correct answer is A Explanation: The contents of the array oldList have not been changed as result of invoking the reverse method. Initially, list refers to the same heap as oldList array through pass-by-sharing; then newList is generated and stored in a different heap; by list = newList, list now refers to the same heap as newList, and list is no longer related to oldList any more.

6.7 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 D. i + 6.5 E. Math.random() * 100

ABC

6.38 Which of the following statements are correct to invoke the printMax method in Listing 6.5 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});

ABC The correct answer is ABC Explanation: The last one printMax(new int[]{1, 2, 3}); is incorrect, because the array must of the double[] type.

6.23 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.

The correct answer is C Explanation: The value stored in x is final, but the values in the array are not final.

6.31 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.

The correct answer is C Explanation: new double[3]{1, 2, 3} should be replaced by new double[]{1, 2, 3}) (anonymous array).

6.45 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

The correct answer is E 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.