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ARRAYS CLASS EXERCISE 1 SOLUTION 1. Write a program that reads in a set of integers from the user, storing them in an array, then prints them out in reverse order. ASSUME 10 NUMBERS… public class ReverseNumbers { static BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); public static void main(String[] args) { // DECLARE & CREATE ARRAY int[] numbers = new int[10]; System.out.println(“The size of the array: “ + numbers.length); // PROMPT USER FOR ARRAY VALUES for (int index = 0; index < numbers.length; index++) { System.out.print(“Enter number “ + (index + 1) + “: “); numbers[index] = Integer.parseInt(keyboard.readLine()); } // DISPLAY CONTENTS OF ARRAY IN REVERSE ORDER System.out.println(“The numbers in reverse: “); for (int index = number.length-1; index >= 0; index--) System.out.print(numbers[index] + “ System.out.println(); } } 1 “); 2. Write a program that prompts the user to make a choice for a pizza size S, M, L or X – and then displays the price as R6.99, R8.99, R12.50 or R15.00 accordingly. You will need to create 2 arrays!! public class Choice { static BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); public static void main (String args[]) throws Exception { char[] sizes = {'S','M','L','X'}; double[] prices = {6.99,8.99,12.50,15.00}; char selection; System.out.print("Enter pizza size (S,M,L,X): "); selection = (keyboard.readLine()).charAt(0): for (int index = 0; index < 4; index++) if (selection == sizes[index]) { System.out.println("The price is " + prices[index]); return; } System.out.println("Invalid Entry"); } } 2 3. Create an array that stores 20 prices, such as 2.34, 7.89, 1.34, and so on. Display the sum of all the prices, and display all values higher than the calculated average value. public class Prices { public static void main (String args[]) { // DECLARE & CREATE ARRAY double[] prices = {2.34,7.89,3.55,6.99,8.99,2.39, 1.29,11.88,56.35,12.33,4.50,1.19,1.79, 2.59,7.10, 9.99,4.55,12.39,4.44,5.55}; double average; double total = 0.0; // CALCULATE TOTAL for (index = 0; index < prices.length; index++) { total += prices[index]; } System.out.println(“Sum of all the prices = “ + total); // CALCULATE AVERAGE average = total / prices.length System.out.println("\nThe average price is " + average + "\n"); // DISPLAY VALUES HIGHER THAN AVERAGE for (index = 0; index < 20; index++) { if (prices[index] > average) System.out.println(prices[i] + " is greater than the average"); } } } 3 4. public class AssignGrade { static BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); // MAIN METHOD public static void main(String[] args) { int numOfStudents = 0; // THE NUMBER OF STUDENTS int[] scores; // ARRAY SCORES int best = 0; // THE BEST SCORE char grade; // THE GRADE // GET NUMBER OF STUDENTS System.out.println(“Please enter number of students”); numOfStudents = Integer.parseInt(keyboard.readLine()); // CREATE ARRAY SCORES scores = new int[numOfStudents]; // READ SCORES AND FIND THE BEST SCORE System.out.println(“Please enter “ + numOfStudents + “ scores”); for (int index = 0; index < scores.length; index++) { scores[index] = Integer.parseInt(keyboard.readLine()); if (scores[index] > best) best = scores[index]; } // ASSIGN AND DISPLAY GRADES for (index = 0; index < scores.length; index++) { if (scores[index] >= best –10) grade = ‘A’; else if (scores[index] >= best –20) grade = ‘B’; else if (scores[index] >= best –30) grade = ‘C’; else if (scores[index] >= best –40) grade = ‘D’; else grade = ‘F’; System.out.println(“Student “ + index + “ score is “ + scores[index] + “ and grade is “ + grade); } } } 4 NOTE: The scores is declared as an array of int type in order to store scores. At the time this array is declared, its size is undetermined. After the user enters the number of students into numOfStudents, an array with the size of numOfStudents is created. The array is not needed to find the best score, but it is needed to keep all of the scores so that grades can be assigned later on, and it is needed when scores are printed along with the students’ grades. 5