Chapter 6

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Chapter 6

Arrays

This activity contains 15 questions.

Consider this code fragment. What geometric figure best describes the array that it constructs? Can you make a picture showing its contents?

char ch = 'A';
char[][] ary = new char[5][];

for (int k = 0; k < ary.length; k++) {
    ary[k] = new char[k+1];
    for (int j = 0; j < ary[k].length; j++)
        ary[k][j] = ch++;
}

A trapezoid.A triangle.A rectangle.A square.

What is printed?

public class Array {

	Array() {
		char[] a = { 'a', 'b', 'c', 
					 'd', 'e' };
		change(a);
		System.out.println(new String(a));
		}

	private void change(char[] a) {
		for (int i=0; i

'e' 'd' 'c' 'b' 'a'edcbaabcde'a' 'b' 'c' 'd' 'e'

What is printed?

public class Array {

	Array() {
		char[] chs = { 'a', 'b', 'c',
					   'd', 'e', 'f'
					 };
		String s = new String(chs, 1, 3);
		System.out.println(s);
	}

	public static void main(String[] args) {
		new Array();
	}
}

cdebcdabcbc

What is printed?

public class Array {

	Array() {
		int[] a = create(2047461578);
		System.out.println(evs(a));
		}

	private int evs(int[] a) {
		int n = 0;
		for (int i=0; i 0) {
			nn /= 10;
			++cnt;
		}
		int[] a = new int[cnt];
		for (int i=0; n>0; i++) {
			a[i] = (int) (n % 10);
			n /= 10;
		}
		return a;
	}

	public static void main(String[] args) {
		new Array();
	}
}

10465

What is printed?

public class Array {

	Array() {
		int[] a = create(24746, 5);
		int[] b = create(35879, 5);
		System.out.print(less(a, b) + " ");
		a = create(247461, 3);
		b = create(358790, 3);
		System.out.println(less(b, a));		
		}

	private int[] create(int n, int lth) {
		int[] a = new int[lth];
		for (int i=0; i= b[i]) {
				isLess = false;
				break;
			}
		return isLess;
	}

	public static void main(String[] args) {
		new Array();
	}
}

true truefalse truetrue falsefalse false

What is printed?

public class Array {

	Array() {
		int[] a = create(5);
		System.out.println(calc(a));
	}

	int[] create(int n) {
		int[] a = new int[n];
		for (int i=0; i

30141055

What is printed?

public class Array {

	Array() {
		int[] a = create(6);
		arrange(a);
		arrange(a);
		System.out.println(a[0] + " " + a[1]
						   + " " + a[2]);
	}

	int[] create(int n) {
		int[] a = new int[n];
		for (int i=0; i

3 5 11 3 -1-1 -3 13 1 5

What is printed?

public class Array {

	Array() {
		int[][] a = create(6);
		int i = a.length - 1;
		for (int j=1; j<=i; j++)
			System.out.print(a[i][j] + " ");
		System.out.println();
	}

	int[][] create(int n) {
		int[][] a = new int[n][];
		a[1] = new int[3];
		a[1][1] = 1;
		for (int i=2; i

1 4 6 4 11 4 6 6 4 11 3 3 11 5 10 10 5 1

What is printed?

public class Array {

	Array() {
		double[] ary = make(7);
		System.out.println(ary[3]);
	}

	double[] make(final int length) {
		double[] ary = new double[length];
		for (int j = 0; j < length; j++)
			ary[j] = j + 3;
		return ary;
	}

	public static void main(String[] args) {
		new Array();
	}
}

6.0Nothing - doesn't compile due to syntax error.7.03.0

What is printed?

public class Array {

	Array() {
		int[] array = new int[12];
		for (int n=0; n

162594

What is printed?

public class Array {

	Array() {
		int[] ary = { 3, 1, 4, 5, 9 };
		bump(ary);
		dump(ary);
	}

	void bump(int[] ary) {
		for (int n=0; n

9 3 12 15 9 23 1 4 5 9 29 3 12 15 27 69 3 12 5 9 2

What is printed?

public class Array {

	Array() {
		int[] ary12 = new int[12];
		int[] ary6 = 
					new int[ary12.length/2];
		for (int n=ary6.length; n>0; n--)
			ary6[n-1] = n + n;
		for (int n=0; n

615110171

Which if statement should be inserted into the code below to make the fragment create the transpose of the 2-D array? A transpose has the property that

Transpose[j][k] = Original[k][j].

int[][] twod = { { 1, 2, 3 },
				 { 4, 5, 6 },
				 { 7, 8, 9 }
			   };

final int LIM = twod.length;
for (int j = 0; j < LIM; j++)
	for (int k = 0; k < LIM; k++)
		if ( ???? ) {
			int x = twod[j][k];
			twod[j][k] = twod[k][j];
			twod[k][j] = x;
		}

if (j != k)if (k != j)if (j > k)if (j = = k)

Which of these methods will sort an array of floats into ascending order?

void arrange(float[] ary) {
	for (int n=0; n

		
	
		

                 
		
			
			void arrange(float[] ary) {
	for (int n=0; n ary[k])
				float x = ary[n];
				ary[n] = ary[k];
				ary[k] = x;
}


		
	
		

                 
		
			
			void arrange(float[] ary) {
	for (int n=1; n<=ary.length; n++)
		for (int k=n; k ary[k]) {
				float x = ary[n];
				ary[n] = ary[k];
				ary[k] = x;
			}
}


		
	
		

                 
		
			
			void arrange(float[] ary) {
	for (int n=0; n ary[k]) {
				float x = ary[n];
				ary[n] = ary[k];
				ary[k] = x;
			}
}

Which statement is true after this program executes?

public class Array {

	Array() {
		String[] ary = new String[6];
		load(ary);
		dump(ary);
	}

	void load(String[] ary) {
		for (int n=1; n

Line three displays: Neg: -3Five lines are printed.Line four displays: Neg: -4Line four displays: Pos: 4

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Chapter 6

What is printed?
public class Array { Array() { char[] chs = { 'a', 'b', 'c', 'd', 'e', 'f' }; String s = new String(chs, 1, 3); System.out.println(s); } public static void main(String[] args) { new Array(); } }

What is printed?
public class Array { Array() { int[] array = new int[12]; for (int n=0; n

Which of these methods will sort an array of floats into ascending order?

Chapter 6

What is printed? public class Array { Array() { char[] chs = { 'a', 'b', 'c', 'd', 'e', 'f' }; String s = new String(chs, 1, 3); System.out.println(s); } public static void main(String[] args) { new Array(); } }

What is printed? public class Array { Array() { int[] array = new int[12]; for (int n=0; n

Which of these methods will sort an array of floats into ascending order?

What is printed?
public class Array { Array() { char[] chs = { 'a', 'b', 'c', 'd', 'e', 'f' }; String s = new String(chs, 1, 3); System.out.println(s); } public static void main(String[] args) { new Array(); } }

What is printed?
public class Array { Array() { int[] array = new int[12]; for (int n=0; n