Quiz on Chapter 7

(answers)

1.What does the computer do when it executes the following statement? Try to give as complete an answer as possible.

Color[] palette = new Color[12];

2.What is meant by the basetype of an array?

3.What does it mean to sort an array?

4.What is the main advantage of binary search over linear search? What is the main disadvantage?

5.What is meant by a dynamic array? What is the advantage of a dynamic array over a regular array?

6.Suppose that a variable strlst has been declared as

ArrayList<String> strlst = new ArrayList<String>();

Assume that the list is not empty and that all the items in the list are non-null. Write a code segment that will find and print the string in the list that comes first in lexicographic order. How would your answer change if strlst were declared to be of type ArrayList instead of ArrayList<String>?

7.What is the purpose of the following subroutine? What is the meaning of the value that it returns, in terms of the value of its parameter?

static String concat( String[] str ) { if (str == null)

return ""; String ans = "";

for (int i = 0; i < str.length; i++) { ans = ans + str[i];

return ans;

}

8. Show the exact output produced by the following code segment.

char[][] pic = new char[6][6]; for (int i = 0; i < 6; i++)

for (int j = 0; j < 6; j++) {

if ( i == j || i == 0 || i == 5 ) pic[i][j] = ’*’;

else

pic[i][j] = ’.’;

}

for (int i = 0; i < 6; i++) { for (int j = 0; j < 6; j++)

System.out.print(pic[i][j]);

System.out.println();

}

9.Write a complete subroutine that finds the largest value in an array of ints. The subroutine should have one parameter, which is an array of type int[]. The largest number in the array should be returned as the value of the subroutine.

10.Suppose that temperature measurements were made on each day of 1999 in each of 100 cities. The measurements have been stored in an array

int[][] temps = new int[100][365];

where temps[c][d] holds the measurement for city number c on the dth day of the year. Write a code segment that will print out the average temperature, over the course of the whole year, for each city. The average temperature for a city can be obtained by adding up all 365 measurements for that city and dividing the answer by 365.0.

11. Suppose that a class, Employee, is defined as follows:

class Employee { String lastName; String firstName; double hourlyWage;

int yearsWithCompany;

}

Suppose that data about 100 employees is already stored in an array:

Employee[] employeeData = new Employee[100];

Write a code segment that will output the first name, last name, and hourly wage of each employee who has been with the company for 20 years or more.

12. Suppose that A has been declared and initialized with the statement

double[] A = new double[20];

and suppose that A has already been filled with 20 values. Write a program segment that will find the average of all the non-zero numbers in the array. (The average is the sum of the numbers, divided by the number of numbers. Note that you will have to count the number of non-zero entries in the array.) Declare any variables that you use.