Exercise GradesStatistics (Method): Write a program called GradesStatistics, which reads in n grades (of int between 0 and 100, inclusive) and displays the average, minimum, maximum, median and standard deviation. Display the floating-point values upto 2 decimal places. Your output shall look like: Enter the number of students: 4 Enter the grade for student 1: 50 Enter the grade for student 2: 51 Enter the grade for student 3: 56 Enter the grade for student 4: 53 {50,51,56,53} The average is: 52.50 The median is: 52.00 The minimum is: 50 The maximum is: 56 The standard deviation is: 2.29 The formula for calculating standard deviation is: Hints: public class GradesStatistics { public static int[] grades; // Declare an int[], to be allocated later. // This array is accessible by all the methods. public static void main(String[] args) { readGrades(); // Read and save the inputs in int[] grades printArray(grades); System.out.println("The average is " + average(grades)); System.out.println("The median is " + median(grades)); System.out.println("The minimum is " + min(grades)); System.out.println("The maximum is " + max(grades)); System.out.println("The standard deviation is " + stdDev(grades)); } // Prompt user for the number of students and allocate the global "grades" array. // Then, prompt user for grade, check for valid grade, and store in "grades". public static void readGrades() { ....... } // Print the given int array in the form of {x1, x2, x3,..., xn}. public static void printArray(int[] array) { ....... } // Return the average value of the given int[] public static double average(int[] array) { ...... } // Return the median value of the given int[] // Median is the center element for odd-number array, // or average of the two center elements for even-number array. // Use Arrays.sort(anArray) to sort anArray in place. public static double median(int[] array) { ...... } // Return the maximum value of the given int[] public static int max(int[] array) { int max = array[0]; // Assume that max is the first element // From second element, if the element is more than max, set the max to this element. ...... } // Return the minimum value of the given int[] public static int min(int[] array) { ....... } // Return the standard deviation of the given int[] public static double stdDev(int[] array) { ....... } } Take note that besides readGrade() that relies on global variable grades, all the methods are self-contained general utilities that operate on any given array.

1. Exercise GradesStatistics (Method): Write a program called GradesStatistics, which reads in n grades (of int between 0 and 100, inclusive) and displays the average, minimum, maximum, median and standard deviation. Display the floating-point values upto 2 decimal places. Your output shall look like:
   Enter the number of students: 4
   Enter the grade for student 1: 50
   Enter the grade for student 2: 51
   Enter the grade for student 3: 56
   Enter the grade for student 4: 53
   {50,51,56,53}
   The average is: 52.50
   The median is: 52.00
   The minimum is: 50
   The maximum is: 56
   The standard deviation is: 2.29
   The formula for calculating standard deviation is:
   
   Hints:
   public class GradesStatistics {
   public static int[] grades; // Declare an int[], to be allocated later.
   // This array is accessible by all the methods.
   
   public static void main(String[] args) {
   readGrades(); // Read and save the inputs in int[] grades
   printArray(grades);
   System.out.println("The average is " + average(grades));
   System.out.println("The median is " + median(grades));
   System.out.println("The minimum is " + min(grades));
   System.out.println("The maximum is " + max(grades));
   System.out.println("The standard deviation is " + stdDev(grades));
   }
   
   // Prompt user for the number of students and allocate the global "grades" array.
   // Then, prompt user for grade, check for valid grade, and store in "grades".
   public static void readGrades() { ....... }
   
   // Print the given int array in the form of {x1, x2, x3,..., xn}.
   public static void printArray(int[] array) { ....... }

// Return the average value of the given int[]
public static double average(int[] array) { ...... }

// Return the median value of the given int[]
// Median is the center element for odd-number array,
// or average of the two center elements for even-number array.
// Use Arrays.sort(anArray) to sort anArray in place.
public static double median(int[] array) { ...... }

// Return the maximum value of the given int[]
public static int max(int[] array) {
int max = array[0]; // Assume that max is the first element
// From second element, if the element is more than max, set the max to this element.
......
}

// Return the minimum value of the given int[]
public static int min(int[] array) { ....... }

// Return the standard deviation of the given int[]
public static double stdDev(int[] array) { ....... }
}
Take note that besides readGrade() that relies on global variable grades, all the methods are self-contained general utilities that operate on any given array.

1. Exercise GradesHistogram (Method): Write a program called GradesHistogram, which reads in n grades (as in the previous exercise), and displays the horizontal and vertical histograms. For example:

  0 -  9: ***

 10 - 19: ***

 20 - 29:

 30 - 39:

 40 - 49: *

 50 - 59: *****

 60 - 69:

 70 - 79:

 80 - 89: *

 90 -100: **

                                *                          

                                *                          

  *     *                       *                          

  *     *                       *                       *   

  *     *                 *     *                 *     *  

 0-9  10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-100

Hints:

• Declare a 10-element int arrays called bins, to maintain the counts for [0,9], [10,19], ..., [90,100]. Take note that the bins's index is mark/10, except mark of 100.
• Write the codes to print the star first. Test it. Then print the labels.
• To print the horizontal histogram, use a nested loop:

• for (int binNum = 0; binNum < bins.length; binNum++) { // each row for one bin
• // Print label for each row
• .......
• for (int starNum = 0; starNum < bins[binNum]; starNum++) {  // each column is one star
• .......
• }
• ......  // print newline

}

• To print the vertical histogram, you need to find the maximum bin count (called maxBinCount) and use a nested loop:

• for (int level = maxBinCount; level >= 1; level--) { // each row for one count level
• for (int binNum = 0; binNum < bins.length; binNum++) {  // each column for one bin
• // if (bin's count >= level) print *
•   // else print blank.
• }
• ......  // print newline

}

1. Exercise (Array and Method): Write a program called PrintChart that prompts the user to input n non-negative integers and draws the corresponding horizontal bar chart. Your program shall use an int array of length n; and comprise methods readInput() and printChart(). A sample session is as follows:

Enter number of bars: 4

Enter bar 1 value: 4

Enter bar 2 value: 3

Enter bar 3 value: 5

Enter bar 4 value: 7

**** (4)

*** (3)

***** (5)

******* (7)