Exam 2. CSC 121 MW Class. Lecturer: Howard Rosenthal. April 25, 2016

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1 Your Name: Exam 2. CSC 121 MW Class Lecturer: Howard Rosenthal April 25, 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 do-while iteration must be executed at least once. b. Declaring an array reference variable creates an array object. c. Each row in a two-dimensional array is itself an array. d. Two reference variables can refer to the same array. e. When an array is created each cell of the array is initialized. f. Any iteration that you can perform with a for statement can also be performed with a dowhile statement. g. When a method s return value is void it sends back the value 0. h. Two different methods can call the same method. i. Binary searches are less efficient than linear searches. j. The length of an array is fixed when it is created. k. char data is expressed in bytecode in java. 2. Given the following initialization int [][] array1 = new int [3][10]; The value array1[2].length =. 3. The number of bytes reserved for the array boolean [][] sizearray = new boolean [5][3] is 4. Write a statement that declares and instantiates a byte array called compy of length 6. 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] =i+1; ref2 =ref1; for (int i=0; i<3; i++) System.out.printf( %b\n, (ref1[i] == ref2[i])); System.out.printf(( %b\n, (ref1==ref2)); 8. What are the values stored in the array a after the following code executes: int [] a = new int [8]; for (int i = 1; i < a.length; i++) { a[i] = ((i/2)+i)%5; } 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. CalculatePercent (16 points) Write a class called CalculatePercent with the main method and ratiocalc method as described below. Write a main method that performs the following 5 times: a. Reads in four integers b. Calls ratiocalc c. Converts the double value that is returned by ratiocalc to a percent as type double. d. Rounds the percent using Math.round(x) e. Prints out rounded percent in the following format: The calculated rounded percent is result % (note: result should print the actual values) ratiocalc is defined as below: a. Has four int variables as formal parameters b. Returns the ratio of the first parameter over the sum of the four parameters as a double. 4

5 2. FindBigRow (32) Write a class FindBigRow that does the following: a. The main method does the following: 1. Requests from the user the dimensions for a two dimensional array. 2. Calls the method createarray to create a two-dimensional integer array 3. Calls a method arrayfull with a reference to the array created by createarray 4. Calls a method called largestrow with a reference to the array created by createarray 5. Prints out the elements of the two-dimensional array row by row. 6. Prints out a sentence that looks like this: The row with the largest sum is row number row. (row is the actual row returned by largestrow) b. createarray 1. Accepts the dimensions of a two dimensional int array as parameters 2. Creates a two-dimensional int array using the input parameters. 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 0 to 19 d. largestrow 1. Has a two-dimensional int array as its formal parameter 2. Finds the row that has the largest sum for its cells 3. Returns the row number for the row that has the largest sum for its cells 4. (Note, if more than 1 row has the same sum, you can return any row with the greatest sum). 5

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