Chapter 8 Multidimensional Arrays

Section 8.2 Two-Dimensional Array Basics
1.	Which of the following statements are correct?
a.	char[][] charArray = {'a', 'b'};
b.	char[2][2] charArray = {{'a', 'b'}, {'c', 'd'}};
c.	char[2][] charArray = {{'a', 'b'}, {'c', 'd'}};
d.	char[][] charArray = {{'a', 'b'}, {'c', 'd'}};
Key:d

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2.	Assume double[][] x = new double[4][5], what are x.length and x[2].length?
a.	4 and 4
b.	4 and 5
c.	5 and 4
d.	5 and 5
Key:b

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3.	What is the index variable for the element at the first row and first column in array a?
a.	a[0][0]
b.	a[1][1]
c.	a[0][1]
d.	a[1][0]
Key:a

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4.	When you create an array using the following statement, the element values are automatically initialized to 0.

int[][] matrix = new int[5][5];

a.	True
b.	False
Key:a

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5. How many elements are array matrix (int[][] matrix = new int[5][5])?

a. 14
b. 20
c. 25
d. 30
Key:c

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6. Analyze the following code:

public class Test {
  public static void main(String[] args) {
    boolean[][] x = new boolean[3][];
    x[0] = new boolean[1]; x[1] = new boolean[2]; 
    x[2] = new boolean[3];
 
    System.out.println("x[2][2] is " + x[2][2]);
  }
}
a. The program has a compile error because new boolean[3][] is wrong.
b. The program has a runtime error because x[2][2] is null.
c. The program runs and displays x[2][2] is null.
d. The program runs and displays x[2][2] is true.
e. The program runs and displays x[2][2] is false.
Key:e x is a ragged array. (See the section on Ragged Array) x[2] has three elements with default value false.

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7.	Assume int[][] x = {{1, 2}, {3, 4}, {5, 6}}, what are x.length are x[0].length?
a.	2 and 1
b.	2 and 2
c.	3 and 2
d.	2 and 3
e.      3 and 3
Key:c

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8.	Assume int[][] x = {{1, 2}, {3, 4, 5}, {5, 6, 5, 9}}, what are x[0].length, x[1].length, and x[2].length?
a.	2, 3, and 3
b.	2, 3, and 4
c.	3, 3, and 3
d.	3, 3, and 4
e.      2, 2, and 2
Key:b

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Section 8.3 Processing Two-Dimensional Arrays
9.	What is the output of the following program?

public class Test {
  public static void main(String[] args) {
    int[][] values = {{3, 4, 5, 1}, {33, 6, 1, 2}};

    int v = values[0][0];
    for (int row = 0; row < values.length; row++)
      for (int column = 0; column < values[row].length; column++)
        if (v < values[row][column])
          v = values[row][column];

    System.out.print(v);
  }
}

a.	1
b.	3
c.	5 
d.	6
e.      33 
Key:e

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10.	What is the output of the following program?

public class Test {
  public static void main(String[] args) {
    int[][] values = {{3, 4, 5, 1}, {33, 6, 1, 2}};

    int v = values[0][0];
    for (int[] list : values)
      for (int element : list)
        if (v > element)
          v = element;

    System.out.print(v);
  }
}


a.	1
b.	3
c.	5 
d.	6
e.      33 
Key:a

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11.	What is the output of the following program?

public class Test {
  public static void main(String[] args) {
    int[][] values = {{3, 4, 5, 1 }, {33, 6, 1, 2}};

    for (int row = 0; row < values.length; row++) {
      java.util.Arrays.sort(values[row]);
      for (int column = 0; column < values[row].length; column++)
        System.out.print(values[row][column] + " ");
      System.out.println();
    }
  }
}

a.	The program prints two rows 3 4 5 1 followed by 33 6 1 2
b.	The program prints on row 3 4 5 1 33 6 1 2
c.	The program prints two rows 3 4 5 1 followed by 2 1 6 33
d.	The program prints two rows 1 3 4 5 followed by 1 2 6 33
e.      The program prints one row 1 3 4 5 1 2 6 33
Key:d

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12. What is the output of the following code?

public class Test {
  public static void main(String[] args) {
    int[][] matrix =
      {{1, 2, 3, 4},
       {4, 5, 6, 7},
       {8, 9, 10, 11},
       {12, 13, 14, 15}};

    for (int i = 0; i < 4; i++)
      System.out.print(matrix[i][1] + " ");
  }
}

a.	1 2 3 4
b.	4 5 6 7
c.	1 3 8 12
d.	2 5 9 13
e.     3 6 10 14
Key:d

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13. What is the output of the following code?
public class Test5 {
  public static void main(String[] args) {
    int[][] matrix =
      {{1, 2, 3, 4},
       {4, 5, 6, 7},
       {8, 9, 10, 11},
       {12, 13, 14, 15}};

    for (int i = 0; i < 4; i++)
      System.out.print(matrix[1][i] + " ");
  }
}
a. 1 2 3 4
b. 4 5 6 7
c. 1 3 8 12
d. 2 5 9 13
e. 3 6 10 14
Key:b

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Section 8.4 Passing Two-Dimensional Arrays to Methods
14. 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};
e.      return new int[][]{{1, 2, 3}, {2, 4, 5}};
Key:e

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15.	What is the output of the following program?

public class Test {
  public static void main(String[] args) {
    int[][] values = {{3, 4, 5, 1}, {33, 6, 1, 2}};

    for (int row = 0; row < values.length; row++) {
      System.out.print(m(values[row]) + " ");
    }
  }

  public static int m(int[] list) {
    int v = list[0];
    for (int i = 1; i < list.length; i++)
      if (v < list[i])
        v = list[i];
    return v;
  }
}

a.	3 33
b.	1 1
c.	5 6
d.	5 33
e.      33 5
Key:d

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Section 8.8 Multidimensional Arrays
16.	Assume double[][][] x = new double[4][5][6], what are x.length, x[2].length, and x[0][0].length?
a.	4, 5, and 6
b.	6, 5, and 4
c.	5, 5, and 5
d.	4, 5, and 4
Key:a

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17.	Which of the following statements are correct?
a.	char[][][] charArray = new char[2][2][];
b.	char[2][2][] charArray = {'a', 'b'};
c.      char[][][] charArray = {{'a', 'b'}, {'c', 'd'}, {'e', 'f'}};
d.	char[][][] charArray = {{{'a', 'b'}, {'c', 'd'}, {'e', 'f'}}};
Key:ad

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18. What is the output of the following code?
public class Test {
  public static void main(String[] args) {
    int[][][] data = {{{1, 2}, {3, 4}},
      {{5, 6}, {7, 8}}};

    System.out.print(data[1][0][0]);
  }
}
a.	1
b.	2
c.	4
d.	5
e.      6
Key:d

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19. What is the output of the following code?
public class Test {
  public static void main(String[] args) {
    int[][][] data = {{{1, 2}, {3, 4}},
      {{5, 6}, {7, 8}}};

    System.out.print(ttt(data[0]));
  }

  public static int ttt(int[][] m) {
    int v = m[0][0];
    
    for (int i = 0; i < m.length; i++)
      for (int j = 0; j < m[i].length; j++)
        if (v < m[i][j])
          v = m[i][j];
   
    return v;
  }
}
a.	1
b.	2
c.	4
d.	5
e.      6
Key:c