Exam 2. CSC 121 TTH Class. Lecturer: Howard Rosenthal. April 26, 2016

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1 Your Name: Exam 2. CSC 121 TTH Class Lecturer: Howard Rosenthal April 26, 2016 The following questions (or parts of questions) in numbers 1-7 are all worth 3 points each. 1. Answer the following as true or false. a. Every for loop must be executed at least once. b. Every row of a two-dimensional array has its own length. c. An array reference variable of type long can refer to an array of the same number of dimensions of type int. d. The parameters in the header of a method are called actual parameters. e. Different rows in a two-dimensional array can hold different types of data. f. When a boolean array is created all the cells are initialized to the value false. g. Any iteration that you can perform with a while statement can also be performed with a do-while statement. h. Every method must return a value. i. Binary searches require that the list first be sorted. j. The length of a one-dimensional array is one greater than the number of cells of the array. k. Input to the JVM is in Unicode format. 2. Given the following initialization int [][] array1 = new int [7][4]; The value array1.length =. 3. The number of bytes reserved for the array double [][] darray = new double [3][4] is 4. Write a statement that declares and instantiates a float array called floatarray of length 12. 1

2 5. Give two different examples of method overloading that display two different ways that methods can be overloaded. (Each example requires two methods with the same name) a. b. 6. Write a single statement the declares, instantiates and initializes an array of type short called shortarray equivalent to the following table:

3 7. What is the printout from the code segment below: int [] ref1 = new int [3]; int [] ref2; for (int i=0; i<3; i++) ref1[i] =2*i; ref2 =ref1; for (int i=0; i<3; i++) (ref2[i] = ref2[i] -1); for (int i=0; i<3; i++) System.out.println(ref1[i]); 8. What are the values stored in the array a after the following code executes: int [] a = new int [8]; sum =0; for (int i = 1; i < a.length; i++) { a[i] = (i%3) +sum; sum = a[i]; } 3

4 Programs: It is important to follow the instructions in each problem. Note: The second problem is on page 5. two.java files to Do not mail these files until you are done with the entire exam. No second mailing will be allowed 1. CalculateHypotenuse (16 points) Write a class called CalculateHypotenuse with the main method and hypocalc method as described below. Write a main method that performs the following 5 times: a. Reads in a pair of numbers of type double representing the two legs of a right triangle b. Calls hypocalc c. Prints out the hypotenuse as follows: The hypotenuse of a right triangle with side one length side1 and side two length side2 is hypotenuse. hypocalc is defined as below: a. Has two type double variables as formal parameters b. Returns the hypotenuse as a type double. You can use Math.pow to calculate the hypotenuse. Remember hypotenuse = (leg1 2 +leg2 2 ) 1/2 4

5 2. FindProducts (32) Write a class FindProducts that does the following: a. The main method does the following: 1. Requests from the user the number of rows for a two-dimensional array. 2. Calls the method createarray to create a two-dimensional int array 3. Calls a method arrayfull with a reference to the array created by createarray 4. Calls a method called getproducts with a reference to the array created by createarray, and accepts a reference to a one-dimensional array as a return value. 5. Prints out the elements of the two-dimensional array row by row. 6. Prints out a sentence for each row that looks like this: The product of row x is product. (Note: x and product are actual numbers). b. createarray 1. Accepts the rows of a two-dimensional int array as parameters 2. Creates a two-dimensional int array with 4 columns for each row. 3. Returns a reference to the array that was created c. arrayfull 1. Has a two-dimensional int array as its formal parameter 2. Fills a two dimensional int array with random integers from 1 to 10 d. getproducts 1. Has a two-dimensional int array as its formal input parameter 2. Finds the product for each row 3. Returns the product of each row in a one-dimensional array with the product for each row in a corresponding cell. 5

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