Exam 1 Review

1. Exam 1 Review

2. 197 days until the AP Computer Science test

3. Test Taking Skills • Read questions carefully, look for exactly what is being asked. • Scan the entire test to understand what parts look easy and what parts are worth the most points. • Never leave questions blank. Write down anything you can think of that is relevant. Blank answers can’t get partial credit. • Pace yourself. Don’t spend lots of time on a question worth only a few points if you still need to do a question worth lots of points.

4. Exam Review 1. All the following are primitive data types: int, char, double, boolean, String a) TRUE b) FALSE

5. Exam Review 2. The following is an example of an implicit cast: inta = (int) (5.0 / 9.0); a) TRUE b) FALSE

6. Explicit cast vs. implicit cast An implicit cast occurs when the cast is automatically done by the compiler and no code is required. inti = 3; double d = 3; public static compute(double d) {…} compute(42); An explicit cast requires code from the programmer to inform the compiler of the cast. inti = (int)(Math.sqrt(2));

7. Exam Review 3. The concatenation operator is the plus sign. a) TRUE b) FALSE

8. Exam Review 4. Adding a double and an int implicitly converts the int variable to a double and the sum is a double. a) TRUE b) FALSE

9. Exam Review WALKTHROUGH inta = 9; int b = 5; for (inti = 0; i <= a; i++){ b = b + i; a = a - i; } a = b = i =

10. Exam Review 5. What are the values of a and b after the following code is executed? int a = 9; int b = 5; for (inti = 0; i <= a; i++){ b = b + i; a = a - i; } a) a = -36, b = 9 b) a = -36, b = 50 c) a = 3, b = 11 d) a = 9, b = 50 e) a = 9, b = 11

11. Exam Review 6. What is the output of the following code? for (inti = 1; i < 3; i++){ for (int j = 3; j > i; j--){ System.out.print(i+j + " "); } } a) 4 3 5 b) 4 3 5 4 c) 4 3 2 5 4 3 d) 1 3 1 2 2 3 e) 1 3 1 2 2 3 2 2

12. Exam Review 7. Which code will produce the following output? The quick brown fox jumped over the lazy dog. I. System.out.print(“The quick brown fox\njumped over the lazy dog.”); II. System.out.print(“The quick brown fox”); System.out.println(“jumped over the lazy dog.”); III. System.out.print(“The quick brown fox”); System.out.print(“jumped over the lazy dog.”); a) None b) I only c) II only d) III only e) I and II only f) I, II, and III

13. Exam Review WALKTHROUGH public static int method() { int a; for (a = 1; a <= 3; a++) { a = (int)Math.pow(2, a); } return a; } a =

14. Exam Review 8. What does the following method return? public static int method() { int a; for (a = 1; a <= 3; a++) { a = (int)Math.pow(2, a); } return a; } a) 1 b) 4 c) 8 d) 9

15. Exam Review WALKTHROUGH Console: public class Program{ public static void main(String[] args){ inta = 1; intb = 2; swap(a, b); System.out.println(a + " " + b + " "); } public static void swap(int a, int b){ a = b; b = a; System.out.print(a + " " + b + " "); } } a = b = a = b =

16. Exam Review 9. What is the output of the following program? public class Program{ public static void main(String[] args){ inta = 1; intb = 2; swap(a, b); System.out.println(a + " " + b + " "); } public static void swap(int a, int b){ a = b; b = a; System.out.print(a + " " + b + " "); } } a) 1 2 2 1 b) 2 2 1 2 c) 2 1 2 1 d) 2 2 2 2 e) 1 2 2 2

17. Exam Review 10. What is the output of the following code? String str = "This is a string."; String newStr = str.substring(str.indexOf('s'), str.indexOf('g')); System.out.println(newStr); intindexOf(String str) Returns the index within this string of the first occurrence of the specified substring. String substring(intbeginIndex, intendIndex) Returns a new string that is a substring of this string, from beginIndex to endIndex(not including the character at endIndex).

18. Exam Review 10. What is the output of the following code? String str = "This is a string."; String newStr = str.substring(str.indexOf('s'), str.indexOf('g')); System.out.println(newStr); a) s is a strin b) s is a string c) strin d) string

19. Exam Review 1. For each expression in the left-hand column, indicate its value in the right-hand column. Be sure to list a constant of appropriate type (e.g., 7.0 rather than 7 for a double, Strings in quotes). (Note that all are worth 3 points except for a, which is worth 2 points) a. 10 + 3 * 5/3 b. 2.1 * 3.141 * (3/12) + 1.5 c. 75 % 10 + 3 % 10 - 12 % 3 d. 2 * 3 + "." + (8 + 4) + 3 * 3 e. 982/10/10/2.0 * 2 + 21/5 f. 9768 % 10 % 10 g. 3 + 2 + “+” + 3 + 2

20. Exam Review 10 + 3 * 5/3 2.1 * 3.141 * (3/12) + 1.5 10 + 15 / 3 10 + 5 15 2.1 * 3.141 * 0 + 1.5 0 + 1.5 1.5

21. Exam Review 75 % 10 + 3 % 10 - 12 % 3 2 * 3 + "." + (8 + 4) + 3 * 3 5 + 3 - 0 8 2 * 3 + “.” + 12 + 3 * 3 6 + “.” + 12 + 9 “6.” + 12 + 9 “6.12” + 9 “6.129”

22. Exam Review 982/10/10/2.0 * 2 + 21/5 98 / 10 / 2.0 * 2 + 21 / 5 9 / 2.0 * 2 + 21 / 5 4.5 * 2 + 21 / 5 9.0 + 4 13.0

23. Exam Review 9768 % 10 % 10 3 + 2 + “+” + 3 + 2 8 % 10 8 5 + “+” + 3 + 2 “5+” + 3 + 2 “5+3” + 2 “5+32”

24. Exam Review 2. (12 points) What is the output of the following program? pubic static void main (String args[]) { intone = 1; inttwo = 2; double three = 3.0; one = theMethod (one, 2, three) + theMethod(1, two, 1.0) + theMethod(one, two, three); System.out.println("one + two is " + (one + two)); } public static inttheMethod(int one, int two, double three) { intreturnValue = (int) (one + two - three); System.out.println(returnValue); return returnValue; }

25. Exam Review WALKTHROUGH pubic static void main (String args[]) { intone = 1; int two = 2; double three = 3.0; one = 0+ 2+ 0; System.out.println("one + two is " + (one + two)); } public static inttheMethod(int one, int two, double three) { intreturnValue = (int) (one + two - three); System.out.println(returnValue); return returnValue; }

26. Exam Review 0 2 0 one + two is 4 Rubric 3 points for each correct line of output 1 point for having “one + two is” in your answer

27. Exam Review 3. (18 points) The usual rules for changing standard English into Pig Latin are as follows: For words that begin with a consonant, the initial consonant is moved to the end of the word, and "ay" is added, as in the following examples: "happy" → "appyhay" "duck" → "uckday” For words that begin with a vowel, you just add "way" to the end. Examples: "egg" → "eggway" "inbox" → "inboxway" Write 2 methods which convert an English word to Pig Latin. Both methods take an input parameter which is a single English word. The method should return the Pig Latin word. Do not worry about other Pig Latin rules for this question.

28. Exam Review public static String englishToPigLatin_ConsonantAtStart( String englishWord) { return word.substring(1) + return.charAt(0) + “ay”; } Rubric: 1 point for using substring(), 3 for getting it correct. 1 point for using charAt(), 3 for getting first char correctly. May use substring(0,1) for full credit. 1 point for concatenating the “ay” strings together, 3 for concatenating correctly. 1 point for using the return statement to return a string, 3 points for returning the correct string

29. Exam Review public static String englishToPigLatin_VowelAtStart( String englishWord) { return word + “way”; } Rubric: 1 point for concatenating the “way” strings together, 3 for concatenating correctly. 1 point for using the return statement to return a string, 3 points for returning the correct string.

30. Exam Review public static String englishToPigLatin_VowelAtStart( String englishWord) { return word + “way”; } Rubric: 1 point for concatenating the “way” strings together, 3 for concatenating correctly. 1 point for using the return statement to return a string, 3 points for returning the correct string.

31. Exam Review 4. (20 points) Write a program which reads the size of a triangle from standard input and prints a "number triangle" of that size, as per the following examples: Size of triangle: 3 321 21 1 Size of triangle: 5 54321 4321 321 21 1

32. Exam Review public static void main(String[] args) { Scanner console = new Scanner(System.in); System.out.print(“enter triangle size: “); intsize = console.nextInt(); triangles(size); console.close(); } Rubric 2 points for correctly declaring the Scanner. 1 point for trying to declare a scanner. 1 points for closing the Scanner.  2 points for user prompt. 2 points for reading in an integer from the Scanner. 1 point for calling console.nextInt(). 1 for assigning to an int correctly.

33. Exam Review public static void triangles(int n) { for (inti = n; i > 0; i--) { for (int j = i; j > 0; j--) { System.out.print(j); } System.out.println(); } } Rubric 6 points for correct outer for loop -2 points each for the initialization, test and update of the for loop 6 points for inner inner for loop -2 points each for the initialization, test and update of the for loop If done incorrectly, 1 point for each for-loop they have. 1 point for the correct output

34. Homework • Read 3.1 • Self Check 4.1, 4.2, 4.4, 4.5, 4.6, 4.13, 4.14 • Exercise 4.3, 4.4 • FracCalc Checkpoint 1