CSIS-120 Final Exam Fall 2015 Name:

Transcription

1 1. Which line of code creates a Player object called player1 using the default constructor a) Player player1; b) Player player1 = new Player (); c) Player1 Player(); d) Player player1 = new Player ; e) player1 = new Player; 2. Which line of code correctly calls the getaverage method on the player1 object a) double ave = player1(getaverage); b) double ave = player1.getaverage; c) double ave = getaverage(player1); d) double ave = player1[getaverage]; e) double ave = player1.getaverage(); 3. Define an integer variable for storing a player's total number of homeruns. To maximize your credit, give the variable a meaningful name and use the proper styling conventions: int totalhomeruns; 4. Define an array of Player objects for storing a team of players. You only need to define the variable. You do not have to allocate memory. Again, give the variable a meaningful name and use proper styling conventions. Player[] playerlist; 5. Using the variable you defined above, use the proper assignment statement to allocate memory for storing exactly 15 players. playerlist = new Player[15]; 6. [2] Using the variable you defined above, assign the last location of the array to the player1 object.. playerlist[14] = player1; playerlist[playerlist.length] = player1; 7. Write the code to define a new Scanner object called in that will read input typed in the terminal window. Scanner in = new Scanner(System.in); 8. Find the errors in the code below and fix them in the space provided: String answer = in.next(); while (answer = "y" "Y") { game.play(); String answer = in.next(); Show corrected code here: String answer = in.next(); while (answer.equals("y") answer.equals("y") ) { game.play(); answer = in.next(); Consider an array of integers called list (shown above) where the indices are shown above the values: What is the output of the following code: System.out.print(list[3]); System.out.println(list[4]); for (int i = 1; i < 3; i++) System.out.print(list[i]); System.out.println(list[list[0]]);

2 10. What is the output of the following code: int x = 5; int y = x + 3; double z = 2.5; System.out.println(x*y-2); System.out.println(x*(y-2)); System.out.println(x/z); System.out.println("-----"); System.out.println(y/x); System.out.println(x < y); System.out.println("x + y = " + x + y); true x + y = Consider this code and answer questions a-e below: Airplane p1 = new Airplane("747"); int rows = 42; int seatsperrow = 10; p1.configurecabin(rows, seatsperrow); System.out.println(p1.getCapacity()); a) How many variables are defined? 3 (p1, rows, seatsperrow) b) What is the data type of the p1 identifier? Airplane 12. Write the implementation of the Airplane class from problem 11. It should have three fields: (1) the type of plane (2) the number of rows (3) the number of seats per row The type of plane is set by the constructor. The number of rows and seats per row are set by the configurecabin method. The getcapacity method returns the total number of seats, which should be an obvious calculation based on rows and seats per row. You only need to implement the class definition, the constructor and two methods described above. public class Airplane { String type; int numofrows; int seatperrow; public Airplane(String t) { type = t; public void configurecabin(int r, int s) { numofrows = r; seatperrow = s; public int getcapacity() { return numofrows*seatperrow; c) What is the data type of the constructor's parameter String d) How many parameters does the getcapacity method take? 2 e) The configurecabin method is most likely a a) Constructor b) Mutator c) Accessor d) Both a Mutator and Accessor e) Neither a Mutator or Accessor 2

3 13. What code is needed in order to use the Scanner class in a program? import java.util.scanner; 14. Fix the syntax and logic errors in the code blocks below int x = 0.5; if (x < 0 x > 100) { System.out.println("invalid grade"; if (x >= 93) { System.out.println(You got an A"); boolean perfect = false; if (x == 100) { else perfect = true; perfect = false; String lettergrade if (x < 80 && x >= 70) { lettergrade = C; else (x < 70 && x >= 60) else { lettergrade = D; lettergrade = F; 15. The method getscore (see below) returns the score of a player's hand in Blackjack. The score of each hand can be 2 or higher. A score of 21 is called "Blackjack." A score greater than 21 is called a "Bust." A tie occurs when both players' scores are the same, if both players get a Bust, or if both players get Blackjack, otherwise the player with the higher score wins. Write the code to print the outcome of the game ("Tie", "Player 1 Wins" or "Player 2 Wins") and if the players got "Blackjack" or a "Bust." int p1 = player1.getscore(); int p2 = player2.getscore(); if (p1 > 21 && p2 > 21 p1 == p2) { System.out.println("Tie"); else if (p1 > p2) { System.out.println("Player 1 Wins"); else if { System.out.println("Player 2 Wins"); if (p1 > 21) { System.out.println("Player 1 Busts"); else if (p1 == 21) { System.out.println("Player 1 Blackjack "); if (p2 > 21) { System.out.println("Player 2 Busts"); else if (p2 == 21) { System.out.println("Player 2 Blackjack "); 3

4 16. Fill in the code for the expression described below. if x is greater than 50 or less than 40 if ( x > 50 x < 40 ) if value is odd if ( value % 2 == 1 ) if t is between 80 and 90 or t is negative if ( t > 80 && t < 90 t < 0) if old equals 27 and new is not equal to 28 if ( old == 27 && new!= 28 ) 17. Evaluate the following expressions as either true or false based on the following variable values. int n = 10; int m = 2; int k = 3 n <= 10 true false m!= 3 true false (n >= 10) (m < 2) true false!(n > 10) && (m > 1) true false k == 2 n > 5 && m > 1 true false 18. What is the value of gooutside after the code below is executed? true boolean hot = true; boolean humid = false; boolean sunny = true; boolean gooutside = true; if (!sunny) { gooutside = false; else if(hot && humid) { gooutside = false; 19. What is the output of this code fragment below? for (int n = 2; n < 100; n = n * n) { System.out.print(n + " "); System.out.println(n); But, n is not "visible" outside the loop, so "compiler error" is also a correct answer. 20. Rewrite the code above using a while loop int n = 2; while (n < 100) { System.out.print(n + " "); n = n * n; System.out.println(n); 21. What is the output of this code fragment below? boolean mystery = true; int n = 10; while (n > 0) { if (mystery) { System.out.print(n + " "); mystery = false; else { mystery = true; n--; System.out.println(n);

5 22. Write a nested for loop to create a 2*n by n rectangle of X's. For example, if n = 3 then the loop will print a 6 by 3 rectangle shown below. Your program should work for any positive value of n. XXXXXX XXXXXX XXXXXX for (int x = 1; x <= n; x++) { for (int y = 1; y <= 2*n; y++) { System.out.print('X'); System.out.println(); 23. Consider an array of sorted numbers that might contain duplicates. The array could be any size a. Write a loop to print the values in reverse order separated with commas but with the word "and" before the last value. Given the array above, your loop should print: 66, 66, 48, 48, 48, 31, 31, 25, 25 and 25 for (int x = list.length-1; x >= 2; x--) { System.out.print(list[x] + ", "); System.out.println(list[1] + " and " + list[0]); b. Write a loop to count the number of unique values and then print that number. Given the array above, your code should print: Unique values = 4. Your code should work for any sized array. int count = 1; for (int x = 0; x < list.length - 1; x++) { if(list[x]!= list[x+1]) { count++; System.out.println("Unique values = " + count); 5

6 24. Consider a file that contains a list of quiz grades separated by spaces: The file has a maximum of 1000 quiz grades. Write a program that reads the file and computes the average grade with the lowest grade dropped. The program should output the following: Enter file name: grades.txt Lowest grade = 75.0 Quiz average = Hints for gaining partial credit: Prompt the user to enter the file name. Use the file name to create a new FileInputStream object and then use that object to create a new Scanner object. Remember that the file might not exist, so we have to use a special structure to handle a possible error. Use the Scanner's methods to keep looping as long as the file has a next grade to read. As you loop, keep track of the number of grades, sum up the grades and update the lowest grade. At the end of the loop, write an appropriate formula to compute the average grade with the lowest grade dropped. 6

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