Comp 170 Test 1 SAMPLE June 8, 2000

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1 Dr. John G. Del Greco Comp 170 Test 1 SAMPLE June 8, 2000 Name Instructions. There are no special instructions for this sample test. 1. True or False? (a) (b) (c) (d) type int. The integer data type long can store larger integers than the data A byte of memory contains 16 bits. Members of type String are called values whereas members of type double are calledobjects. IfP,Q, andrrepresent conditions such thatp =false,q=true andr=true, then the condition evaluates totrue. 2. Multiple choice. Circle the correct answer.!(p &&Q) ==!P &&!Q (a) Which of the following assigns a value to the integer variable n. 1. n = 35; 2. n = SavitchIn.readLineInt(); 3. int i = n; 4. n == 7%2; 5. all of the above 6. 1 and 2 only (b) Consider the following code fragment. String englishalphabet = abcdefghijklmnopqrstuvwxyz ; char letter = englishalphabet.charat(englishalphabet.length() - 2); Which of the following statements is true? 1. the code fragment is not legal and will generate a compiler error 2. letter is assignedthe blankcharacter 3. letter is assigned z 4. letter is assigned y 5. none of the above (c) The expression55/7%3-2%3-1 evaluates to

2 none of the above 3. Consider the following fragment of code. int a, b, c = 35; a = -2; b = 7; a = a - b; b = b - a; c = (int) Math.sqrt(c); a = a * b; b = b * a; After this fragment is executed, what are the values of the variables a, b and c? 4. Suppose phrase, firsthalf and secondhalf are variables of type String. Write assignment statements thatwill assignfirsthalf the rst half of phrase andsecondhalf the second half of phrase. You may assume that phrase has even length. (Hint: Use the substring methodof the String class.) int n = phrase.length(); //continue from this point 5. Consider the following code fragment. int i = 23; double number = 10.83; char letter; String frag; i = SavitchIn.readLineInt(); number = SavitchIn.readLineDouble(); letter = SavitchIn.readLineNonwhiteChar(); frag = SavitchIn.readLine(); frag = frag + and some by virtue fall Suppose the user inputs the following data. (The character t in the input denotes a blank.) t t t t t t t t$******************$ Some rise by sin, What are the values of the following variables after the code is executed? (a) i = (b) number = 2

3 (c) letter = (d) frag = 6. Write a Java code fragment for each of the following. Assume that i, j, k and p are variables of type int. (a) Assign to p the smallest of the values of i, j and k. (b) Increment i by 1 if the value of j is between 0 and 5 inclusive, increment i by 2 if j is between 6 and 25 inclusive and increment i by 3 if j is between 26 and 100 inclusive. 7. Consider the following fragment of code. int i, j; if (i == j) System.out.println( 1 ); else if ((i % j) < 3) System.out.println( 2 ); else if (i < (j - 1)) System.out.println( 3 ); else System.out.println( 4 ); System.out.println(i + j); What is the output for the input values of i and j listed below? (a) i = 9 and j = 4 (b) i = 4 and j = 9 (c) i = 5 and j = 6 (d) i = -7 and j = Use a switch statement to rewrite the following code fragment. if (i == 1) p = j; else if ((i == 2) jj (i == 3)) p = j + 1; else if (i == 5) p = j - 3; else p = 0; 9. The following Java program was written to input a string and output the number of occurrences of the character * inthe string. Something is wrong with the code below! It does not evencompile correctly let alone run. Identifyall the errors (syntax, logical 3

4 or runtime) in the program and suggest how to correct them. Line numbers have been included for your convenience. (Hint: There are six serious mistakes.) (1.) public class Stars { (2.) public static void main(string [] args) { (3.) System.out.print( Please enter any sequence ); (4.) System.out.println( of characters and press Enter ); (5.) String sentence = SavitchIn.readLine(); (6.) Char star = * ; (7.) int starcount; (8.) int charnumber = 1; (9.) while (charnumber <= sentence.length()); { (10.) if (sentence.charat(charnumber) = star) (11.) starcount++; (12.) charnumber++; (13.) //end of loop (14.) System.out.println( Total number of stars: + starcount); (15.) //end of main (16.) //end of class (a) ERROR #1: (b) ERROR #2: (c) ERROR #3: (d) ERROR #4: (e) ERROR #5: (f) ERROR #6: 10. Fill in the blank so that each loop prints exactly 12 asterisks. (a) int i = 5; while (i > ) { i--; (b) (There is more than one correct answer for the following fragment.) int i = ; do { i = i + 2; while (i < 30); 4

5 11. For each of the following loops, how many times is the asterisk printed? If there is an in nite loop, write INFINITE LOOP. (a) int i = 1, j; while (i <= 5) { j = 0; while (j < i) { j++; i++; (b) The asteriskis printed The asteriskis printed times. int i = 1; do { i--; while (i < 1); times. 12. Complete the coding of lines (5.) and (6.) so that the following program prints out the digits of an integernin reverse order. For example, ifn=58697, then the output should be (Hint: Note that58697=10=5869 and58697%10=7.) (1.) public class ReverseDigits { (2.) public static void main(string [] args) { (3.) int n = SavitchIn.readLineInt(); (4.) while (n > 0) { (5.) System.out.print( ); (6.) n = ; (7.) //end loop (8.) System.out.println(); (9.) //end main (10.) //end class 13. The following program is supposed to compute the sum of the rst n cubes. For example ifn=4, then the sum of the rst four cubes is = = 5

6 100. Complete the coding of lines (6.) and (7.). (1.) public class Cubes { (2.) public static void main(string [] args) { (3.) int n = SavitchIn.readLineInt(); (4.) int sumofcubes = 0; (5.) while (n > 0) { (6.) sumofcubes = sumofcubes + ; (7.) n = n ; (8.) //end loop (9.) System.out.print( Sum of first + n); (10.) System.out.println( cubes = + sumofcubes); (11.) //end main (12.) //end class 14. How many times is the * printed? i = 1; while (i <= 10) { k = 3; while (k <= 6) { m = 2; while (m < 5) { p = 5; while (p <= 9) { System.out.print( * ); p++; m++; k++; i++; 6