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Java Coffee Break

Quiz Questions
For Chapter 8

THIS PAGE CONTAINS A SAMPLE quiz on material from Chapter 8 of this on-line Java textbook. You should be able to answer these questions after studying that chapter. Sample answers to all the quiz questions can be found here.

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

             Color[]  pallette  =  new  Color[12];

Question 2: What is meant by the basetype of an array?

Question 3: What does it mean to sort an array?

Question 4: What is meant by a dynamic array? What is the advantage of a dynamic array over a regular array?

Question 5: 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 null;
         String ans = "";
         for (int i = 0; i < str.length; i++) {
            ans = ans + str[i];
         return ans;

Question 6: 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] = '*';
                   pic[i][j] = '.';
          for (int i = 0; i < 6; i++) {
             for (int j = 0; j < 6; j++)

Question 7: 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.

Question 8: 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.

Question 9: 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.

Question 10: 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.

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