Download week-13-method-revision-complete-example

Method Revision

Problem
 we want to use a java program to analysis the students grades for
csc111 exam, The maximum capacity of the section is 40. the user
should enter number of students first (not larger than 40 ) , then the
grades. Then the program should print the equivalent grade out of
15, also the program should print maximum grade, minimum grade,
average grade. finally the program should print grade distribution
for mid term as bar chart
Problem
 Sample Run
 input :
Enter the number of student less than 40 :
25
Enter 25 grades
67
89
76
…
…
67

output :
The equivalent grade are :
10 13 11 ……………. 11
lowest grade is 4 and the Highest grade is 14
the Average grade is 8.75
Overall grade distribution:
00-04 : ****
05-09 : *************
10-14: *****
15
:*
analysis
 input :
 number of students (num) (should be validated )
 list of grades (grades)
 processing
 calculate equivalent grades
 compute average
 find maximum grade
 find minimum grade
 output :
 equivalent grades
 lowest grade and the Highest grade
 the Average grade
 grade Distribution
using method
Using methods has several advantages:
 While working on one method, you can focus on just that part of the
program and construct it, debug it, and perfect it.
 Different people can work on different methods simultaneously.
 If a method is needed in more than one place in a program, or in
different programs, you can write it once and use it many times.
 Using methods greatly enhances the program’s readability because it
reduces the complexity of the method main.
readGrades
printGrades
calculateEquGrade
findMaxGrade
findMinGrade
calculateAvg
printBarChart
flow chart
Required Methods
Design
start program
average computeAverage(eqGrades)
initialize maxCapacity with 40
print eqGrades
initialize grades [] with size 40
print max
initialize eqGrades [] with size 40
do {read num }while (num>40)
read grades(grades)
print min
print Average
printBarChart (eqGrades)
for each grade(i)
end program
eqGrades[i]=calculateEquGrades (grades[i])
maxFindmaxGrade(eqGrades)
min FindMinGrade(eqGrades)
Program Structure
import java.util.Scanner;
public class gradeBook {
static Scanner console=new Scanner (System.in);
static final int maxCapcity = 40;
static int num;
public static void main (String args []){
//declaration
//input
//processing
//output
}
//methods declaration
}//end of class
writing method
 The name of the method
 The number of parameters, if any
 The data type of each parameter
 The data type of the value computed (that is, the value
returned) by the method.

what should the method do. (method body)
read grades

Read grades in an Array
public static void readGrades(int [] gradeList) {
for (int count = 0; count < num ; count++)
gradeList[count] = console.nextInt();
}

Print grades from an Array
public static void printGrades(int [] gradeList) {
for (int count = 0; count < num ; count++)
System.out.print(gradeList[i]);;
System.out.println();
}
find equivalent
 The name of the method (findEquGrade)
 The number of parameters (grade)
 The data type of each parameter (grade int )
 The data type of the value computed by the method. (eqGrade 
int)

eqGrade = grad/100.0 * 15  should be rounded to nearest int

eqGrade =Math .round(grad/100.0 * 15.0)
find equivalent
public static int findEquGrade(int grade) {
int eqGrade =(int)Math .round(grad/100.0 * 15.0);
return eqGrade ;
}
find maximum grade
 name : findMaxGrade

parameter : grades

parameters data type : int []

return data type : max  int
find maximum grade
public static int findMaxGrade (int [] grades )
{
int max = grades [0];
for (int i= 1; i< num; i++)
max=Math.max(max , grades[i]);
return max ;
}
find minimum grade
public static int findMinGrade (int [] grades )
{
int min =grades [0];
for (int I = 1; i< num; i++)
min=Math.min(min , grades[i]);
return min ;
}
Calculate average

The name of the method (calculateAvg)

The number of parameters ( grades )

The data type of each parameter (grades int [])

The data type of the value computed by the method. (Average  double)

method body :



initialize sum with 0
for each grade(i) in grades
sum+=grades[i];
Average =sum/grades.length
Calculate average
public static double calculateAvg (int [] grades )
{
int sum=0;
for (int i=0;i<num;i++)
sum+=grades[i];
return sum*1.0/num;
}
grade distribution
 Suppose the equivalent grades are
 11, 10, 7, 9, 15, 13, 14, 6, 4, 3
 one grades of 15
 four grades 10-14
 three grades 9-5
 two grades 4-0
 we need to stores this grade distribution in an array of four elements:

each element corresponding to a category of grades

e.g. frequentArray[0]  indicates the number of grade in the range 0-4
calculate grade distribution
if (grades[i] ==15)
0
0
0-4
1
0
5-9
2
0
10-14
3
0
15
++frequentArray[3];
else if (grades[i] <=14 && grades[i]>=10 )
++frequentArray[2];
else if (grades[i] <=9 && grades[i]>=5 )
++frequentArray[1];
else if (grades[i] <=4 && grades[i]>=0)
++frequentArray[0];
calculate grade distribution
 to calculate grade distribution we need to use frequency array
 find the relation between index (0,1,2,3) and grade distribution

index 0->{0,1,2,3,4}
 index 1->{5,6,7,8,9}
For grades: 11, 10, 7, 9, 15, 13, 14, 6, 4, 3
 index 2->{10,11,12,13,14}
0-4
0
2
 index 3->{15}
 ++frequentArray[ grade[i] /5];
1
3
5-9
2
4
10-14
3
1
15
print barChart
public static void printBarChart (int grades[])
{
// find grades distribution
Int freq[]=new int [4];
for (int i=0;i<num; i++)
++freq[grades[i]/5];
//for each freq element, output a bar of chart
for (int i=0; i<freq.length; i++)
{
// output label (“00-04 ”,” ”)
if (i==3) System.out.printf(“%5d: ”, 15);
else System.out.printf(“%02d-%02d: ”,i*5, i*5+4);
//print bar of asterisks
for (int s=0; s<freq[i]; s++)
{System.out.print(“*”);}
System.out.println();//start new line of output
}//end outer for
}// end method
print barChart for specific range
public static void printBarChart
(int grades[], int start, int end )
{// find grades distribution
int freq=0;
//for each freq element, output
a bar of chart
for (int i=0;i<num; i++)
{
if (grades[i] <=end&&
grades[i]>=start)
++freq;
}
// output label (“00-04 ”,” ”)
if(start==end )
System.out.printf(“%5d: ”,end);
else System.out.printf(“%02d%02d: ”,start, end);
//print bar of asterisks
for (int
s=0;s<freq;s++){System.out.print(“*”
);
}
System.out.println();//start new line
of output }//end outer for
}// end method
variable and data type
 input :
 num int
 grades int []
 processing
 eqGrades int []
 average  double
 max  int
 min  int
//processing
// find equivalent array
for (int i=0;i<grades.length; i++)
import java.util.Scanner;
eqGrades[i]= findEquGrades(grades[i]);
public class gradeBook {
static Scanner console=new Scanner (System.in); //find Maximum grade
static final int maxCapcity =40;
max =findMaxGrade (eqGrades);
static int num;
//find Minimum grade
public static void main (String args []){
min =findMinGrade (eqGrades);
//declaration
// calculate average
int max ,min ;
average=calculateAvg(eqGrades);
int [] grades, eqGrades;
//output
grades =new int [maxCapcity];
//print equivalent grades
eqGrades=new int [maxCapcity];
System.out.println(“The equivalent grades are”
double average;
printGrades(eqGrades);
//input
System.out.printf(“lowest grade is %d and the
do {
Highest grade is %d %n
System.out.println(“Enter number of students”);
the Average grade is %.2f ”, min, max, average);
num= console.nextInt();
System.out.println(“The Overall grade
while (num>40);
distribution :”);
//read grades from user
//print bar chart
System.out.println(“Enter the grades ”);
printBarChart (eqGrades);
readGrades(grades);
} //end main
// method declaration
public static void readGrades(int [] gradeList) {
for (int count = 0; count < num; count++)
gradeList[count] = console.nextInt();}
public static int findEquGrades(int grade) {
int eqGrade =(int)Math .round(grade/100.0 *
15.0);
return eqGrade ;}
public static int findMaxGrade (int [] grades )
{int max =grades [0];
for (int i=1;i<num;i++)
max=Math.max(max,grades[i]);
return max ;}
public static int findMinGrade (int [] grades )
{int min =grades [0];
for (int i=1;i<num;i++)
min=Math.min(min,grades[i]);
return min ;}
public static void printGrades(int [] grades )
{for (int i=0;i<num;i++)
System.out.print(grades[i]+” ”);
System.out.println();}
public static void printBarChart (int grades[])
{// find grades distribution
int freq[]=new int [4];
for (int i=0;i<num; i++)
++freq[grades[i]/5];
//for each freq element, output a bar of chart
for (int i=0;i<freq.length; i++)
{// output label (“00-04 ”,” ”)
if(i==3) System.out.printf(“%5d: ”,15);
else System.out.printf(“%02d-%02d: ”,i*5, i*5+4
//print bar of asterisks
for (int s=0;s<freq[i];s++)
{System.out.print(“*”);}
System.out.println();//start new line of output
}//end outer for }// end method
public static double calculateAvg (int [] grades )
{int sum=0;
for (int i=0;i<num;i++)
sum+=grades[i];
return sum*1.0/grades.length;
//return (double) sum/grades.length;}