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Extra Exercises

Extra Exercises. Sources http://www.seas.upenn.edu/~cse110/exams/old/midterm1_fall05.pdf http://www.csd.uwo.ca/courses/CS026b/oldmidt/midterm.doc. Value of The Variable x. For each of the following program fragments, what is the value of the variable x after the statements execute?. (A)

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Extra Exercises

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  1. Extra Exercises Sources http://www.seas.upenn.edu/~cse110/exams/old/midterm1_fall05.pdf http://www.csd.uwo.ca/courses/CS026b/oldmidt/midterm.doc

  2. Value of The Variable x • For each of the following program fragments, what is the value of the variable x after the statements execute? (A) int y = 5; int x = y; y = y * 2; (B) int x = 5; x = x / 2; x = x + 3 * x - 3;

  3. Value of The Variable x • For each of the following program fragments, what is the value of the variable x after the statements execute? (C) double x = 13 / 2; (D) boolean x = ( 2 == 3 );

  4. Value of expressions • What is the value of each of the following valid expressions? (a) (2 < 2) || (2 > 2) (b) (!false) && (!false) (c) ( 5 > 2 ) == ( 3 <= 3 )

  5. Debug According to Description • Fix the code so that it works according to the supplied documentation (in comments) /* Calculates sum of all of the even * numbers from 0 to limit inclusive. * Assumes limit is initialized above * to a positive integer. */ int i = 0; int sum = 0; while (i != limit) { sum = sum + i; i+=2; }

  6. Debug According to Description • Solution /* Calculates sum of all of the even * numbers from 0 to limit inclusive. * Assumes limit is initialized above * to a positive integer. */ int i = 0; int sum = 0; while (i <= limit) { sum = sum + i; i+=2; }

  7. How Many Iterations? • How many times the body of the loop is executed? • 0, 1, infinite, or “> 1”? • ”> 1” means more than once but not infinite. int x=1; while (x<10) { System.out.println(x); }

  8. How Many Iterations? • How many times the body of the loop is executed? • 0, 1, infinite, or “> 1”? • ”> 1” means more than once but not infinite. int x=10; while(x<10) System.out.println(x); x=x-1;

  9. How Many Iterations? • If we put a ; at while loop • How many times x is printed? int x=10; while(x<10); System.out.println(x); x=x-1;

  10. How Many Iterations? • How many times the body of the loop is executed? • 0, 1, infinite, or “> 1”? • ”> 1” means more than once but not infinite. int x=1; while(x!=10) { x = x*2; }

  11. True/False • In Java I can have both mystring and myString as two distinct variables in same program. • When writing a computer program, everything must be precise and unambiguous. • The starting index position for a string in Java is 0. • When a program written in Java is compiled, it is typically compiled to bytecode

  12. Multiple Choice 1 In Java, the calculation 3 % 4 produces a result of: a. 0 b. 1 c. 0.75 d. 3 e. None of the above.

  13. Multiple Choice Which of the following represents a character in Java: a. a b. 'a' c. "a" d. All of the above. e. None of the above.

  14. Multiple Choice Which of the following is a valid way to create a String object containing the text “Hello there” in Java: a. String tempString = "Hello there"; b. String tempString = "Hello" + " " + "there"; c. String tempString = new String("Hello there"); d. All of the above. e. None of the above.

  15. Value and Type • For each of the following Java expressions, provide the result of evaluating the expression, and identify the type of this value. a. "Java" + "is" + "great" b. "123 + 456" c. 3 / 2 * 1.0 d. "The answer is: " + 5 + 5 e. "The answer is: " + (5 + 5)

  16. Value and Type • For each of the following Java expressions, provide the result of evaluating the expression, and identify the type of this value. f. 'b' > 'a' g. 1 + 2 * 3 – 4 / 5 h. (((int) 1.0) % 5 + 0.5 * 2) / 2.0 – ((double) 1) i. 3 / 6 * (16.3 * 20.2 + 960 / 6.0)

  17. Code Tracing • Trace this code segment and report what this code prints to the screen int numPeople = 4; System.out.println(numPeople); double bill = 100.00; System.out.println(bill); double tip = bill * 0.2; System.out.println(tip); double total = bill + tip; System.out.println(total); double totalPerPerson = total / numPeople; System.out.println(totalPerPerson);

  18. Code Understanding • What does this code do? int sum = 0; int i = 51; while (i < 100) { sum = sum + (i*i); i++; i++; }

  19. Code Understanding • What does this code do? int sum = 0; int i = 51; while (i < 100) { sum = sum + (i*i); i++; i++; }

  20. Fix Code • Fix code to implement a validation loop to ensure that the user enters a number between 1 and 9 inclusive? Scanner in = new Scanner(System.in); int ans; ans = in.nextInt(); while (ans > 0 && ans < 10) { ans = in.nextInt(); }

  21. Code Understanding • What does this code do? String foo = "Java!"; String bar = ""; int i = 0; while( i < foo.length()) { bar = foo.charAt(i) + bar; i++; //i.e i=i+1; } System.out.println(bar);

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