CS110 Lab 14

Introduction to Arrays

PART I

1. Write a definition for an array called nums that will store 4 integers. Initialize this array so that all elements are set to 0.
2. Write a definition for an array called realNums that will store fivefloating-point values. Write additional statements that will assign the value -12.999 to the first and last element in this array.
3. Write a definition for an array called letters that will store 200 characters. Write an additional statement that will assign the value 'H' to the 89th element in this array.
4. Write a definition for an array called grades that will store the grades of 25 students.

PART II

For the following questions, refer to the definitions below.



final int MAX = 10; int [] sample = {2, 3, 5, 1, 8, 4, 9, -3, 6, 3}; int x;





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1. What value is x assigned in the code below?

   x = sample[0];

   
   
   
2. What value is x assigned in the code below?

   x = sample[MAX - 1];

   
   
   
3. What value is x assigned in the code below?

   x = sample[3] * sample[5];

   
   
   
4. What value is x assigned in the code below?

   x = 2 *sample[2] - 3 * sample[7];

   
   
   
5. What does the array sample look like after the following code segment is executed?

   sample[0] = sample[MAX - 1]; sample[MAX - 3] = 7;

   
   
   
6. What does the array sample look like after the following code segment is executed?

   int i = 0; sample[i] = sample[i + 1];

   
   
   
7. What does the array sample look like after the following code segment is executed?

   for (int i = 0; i < sample.length; i++) sample[i]++;

   
   
   
8. What does the array sample look like after the following code segment is executed?

   for (int i = 0; i < MAX - 2; i++) sample[i] = sample[i + 1];

   
   
   
9. Write a segment of code that displays all the values in sample in reverse. Assume you don't know what the stored values in the array are.
   
   
10. Write a segment of code that replaces all odd integer values with the number 7. Assume you don't know what the stored values in the array are.
    
    
11. Write a segment of code that finds the smallest number in the sample array. Assume you don't know what the stored values in the array are.
    
    
12. Write a segment of code that requires the user to input a list of 10 valid test scores in sample. Reject scores that are outside the valid range of 0-100. Compute the average test score and display all the scores that are above the average.
    
    

PART III Passing Arrays to methods

• 1.
  

  					public static void main(String[] args) {
  						int[] arr = { 1, 2, 3 };
  						int x = 5;
  						func(arr, x);
  						System.out.println(Arrays.toString(arr));
  						System.out.println(x);
  					}
  
  					public static void func(int[] arr, int x) {
  						arr[0] = x;
  						arr[1] = x;
  						arr[2] = x;
  						x = 9;
  					}
  				

• 2.
  

  					public static void main(String[] args) {
  						int[] arr = { 1, 2, 3 };
  						int x = 5;
  						func(arr, x);
  						System.out.println(Arrays.toString(arr));
  						System.out.println(x);
  					}
  
  					public static void func(int[] brr, int x) {
  						brr[0] = x;
  					}
  				

• 3.
  

  					public static void main(String[] args) {
  						int[] arr = { 1, 2, 3 };
  						int x = 5;
  						func(arr, x);
  						System.out.println(Arrays.toString(arr));
  						System.out.println(x);
  					}
  
  					public static void func(int[] brr, int x) {
  						int [] arr = {2 , 3 , 1};
  						arr[0] = 7;
  						brr[0] = x;
  					}
  				

• 4.
  

  					public static void main(String[] args) {
  						int[] arr = { 1, 2, 3 };
  						int x = 5;
  						arr = func(arr, x);
  						System.out.println(Arrays.toString(arr));
  						System.out.println(x);
  					}
  
  					public static int [] func(int[] brr, int x) {
  						int [] arr = {2 , 3 , 1};
  						brr[0] = x;
  						return arr;
  					}
  				

• 5.
  

  					public static void main(String[] args) {
  						int[] arr = { 1, 2, 3 };
  						System.out.println(Arrays.toString(arr));
  						arr = func(arr);
  						System.out.println(Arrays.toString(arr));
  					}
  
  					public static int [] func(int[] arr) {
  						int [] brr = new int [arr.length*2];
  						int j = 0;
  						for (int i = 0; i < arr.length; i++){
  							brr[j] = arr[i];
  							j++;
  							brr[j] = arr[i];
  							j++;
  						}
  						return brr;
  					}
  				

PART IV Two-dimensional Arrays

1. Write a method makeSmallest() that receives a two-dimensional array containing integers. Create and return an array containing the smallest number in each row.
2. Write a method makeAverages() that receives a two-dimensional array containing integers. Create and return an array containing the averages of the rows.
3. Write a method matrixMultiply() that receives two integer matrices. Return the result of matrix multiplication.